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Today’s SportSub family of personal submersibles is the culmination of over twenty years of product refinement. Just peruse the numerous technologies listed below and you will begin to appreciate the lengths to which International VentureCraft Corp. will go to provide the safest, most reliable, attractive, easy to use, and exhilarating submersibles available anywhere. The design is both sophisticated and elegant in its simplicity. If that sounds like a paradox - read on and you’ll understand.

A casual inspection of a SportSub makes it look deceptively simple. It’s very attractive but doesn’t look very complicated or high-tech. Looking up from below, the hull appears to be nothing more than an open shell. What keeps water out of the cockpit? Why is there a big hollow nose with an open bottom? This sub must be just a capsule that SCUBA divers use to drive around while wearing their breathing apparatus! Why not just use a dive puller?

It’s because of misconceptions like these that we proudly present the worlds most sophisticated and practical submersible technology for recreational, commercial and shallow industrial operations.


The basic principle of the ambient pressure submersible is the same as a diving bell. It’s like taking a giant drinking cup and turning it upside down and pushing it under water. The air trapped inside stays there as long as you don’t tip it too far sideways. The bottom is open to the water so the internal pressure and the external pressure are always equal. The SportSub design ensures that the air pocket trapped in its cockpit never shrinks or expands as pressure changes during descends or ascends. If the air pocket volume were allowed to shrink or expand with changing pressure the buoyancy would change, causing a loss of control. This is regulated by the SportSub’s automatic buoyancy control system, which maintains neutral buoyancy throughout a dive.


Neutral buoyancy does not equal neutral stability however. The SportSub is kept in a stable, upright position at all times because its center of buoyancy and center of gravity are as far apart as possible, causing a sort of pendulum effect. The bottom of the SportSub is where the majority of its weight is located and the top is where the buoyant air pocket is located. This causes a very strong tendency for the bottom of the sub to stay directly under the top, and prevents any air from spilling out the bottom of the cockpit.

Buoyancy Range

SportSubs can be configured to ride high on the surface, with the entire cockpit and upper hull above water, submerged at neutral buoyancy, or landed solidly on the bottom with enough weight to keep them there while the occupants exit for an extra-vehicular excursion. All of this can be accomplished with a range of combined passenger weights up to 600 pounds in the three-seat models.

Buoyancy adjustment is accomplished by flooding or blowing water ballast within three separate ballast tanks. Flood valves in the cockpit allow air to escape out the tops of each ballast tank while water floods in through their open bottoms. Blowing ballast reverses this procedure, requiring the flood valves to be closed while blow valves are opened to allow pressurized air to bubble into the tanks, rising to the top and forcing water out the open bottom. The forward ballast tank is the hollow, bottomless nose. The entire tail section, surrounding the main air supply tanks, is the aft ballast tank, and the cockpit itself is the third tank.

To ride high on the surface all three tanks are filled to capacity with air. To submerge, both fore and aft ballast tanks are completely flooded while the air volume in the cockpit is adjusted such that neutral buoyancy is achieved at the occupant’s weight. To land on the bottom, the cockpit air volume is adjusted to its minimum, providing maximum negative buoyancy.


It might be nice for a SportSub to have an entry and exit hatch at its highest point so passengers could climb in and out above the water. There are several advantages, however, to the swim-in method we chose.

The greatest advantage is safety. The simple rear opening can never get stuck or jammed shut, trapping occupants inside. It is also immune to leaking. If a hatch at the top of the cockpit were to leak, all the air would escape and buoyancy would be lost. A third safety feature of the swimming entry is to ensure that occupants are not prone to panic. Having to enter the sub by swimming into the cockpit is a nice way to help prevent passengers from taking a ride if they aren’t comfortable under water. This gives the operator some confidence that passengers will be capable of handling a 'worst case' emergency situation.

Another benefit of the open hatch approach is cost. Our solution is free! A good quality sealed submarine hatch could easily cost as much as an entire SportSub.


It seems logical to assume that more windows would provide better visibility. This is not the case under water, for two reasons; reflection, and refraction.

Most underwater environments are dimly lit as light filters down from the surface. This surface light must be kept out of the cockpit or it will cause reflections. It would be somewhat like driving a car at night with the interior light on. Anything bright in the cockpit would be reflected by the front windows, causing a ghost image to appear in the pilot’s field of view.

The SportSub’s balanced pressure hull allows large, flat windows to be used because they don’t have to withstand much pressure difference. Flat windows minimize the natural distortion, called refraction, which occurs when water and air meet. These are used for forward-looking windows to permit accurate visual navigation. The dome shaped side windows exploit the distortion effect and provide a wide-angle lens effect allowing occupants to see a larger vista.

Breathing Air Quality

Fresh air is continually circulated through the cockpit during a dive. Airflow is regulated by a flow meter which is set by the pilot according to a formula, depending on how many occupants are in the SportSub. This formula was developed through extensive research done by scientists and medical doctors using a SportSub cockpit in a hyperbaric chamber. All breathing gasses were monitored while different sized subjects occupied the cockpit in the chamber. Male and female subjects were tested, both at rest and under conditions of controlled exertion. The chamber was set to various pressures to simulate different depths. The formula was derived to provide adequate airflow for worst-case conditions. During normal operation of a SportSub there is much more air circulation through the cockpit for buoyancy control than from the flow meter so there is never a lack of fresh air.

Pressure Compensated Dry Compartments

There are a number of compartments within the SportSub that contain components that will deteriorate rapidly if they get wet. These compartments are the control panel, battery box, junction box and thruster motors. Keeping these areas dry requires compartments with either enough strength to withstand the pressures at the maximum dive depth or a means of pressure balancing. The SportSub regulates these compartments so that they are at a pressure just slightly above that of the surrounding water. This ensures that any leak will allow air to escape rather than water to seep in. This accomplishes two things; it keeps components dry even when there is a leak and it makes leak detection easy by watching for a stream of bubbles.

Maneuvering Controls

The SportSub has to maneuver in two dimensions while on the surface, and in three dimensions while submerged. It moves forward, backward, up, down, and can even hover and turn on the spot, a lot like the maneuverability of a helicopter.

All maneuvering is accomplished with only two thrusters, built in to the dive plains, and two control handles. The thrusters are located so that their center of thrust is at the same height on the hull as its center of drag, so there is no tendency to nose up or down with changes in thrust. The hull design also ensures that the dive plane position is below the water line when the SportSub is high on the surface.

One of the pilot’s hands controls the speed and direction of both thrusters simultaneously, using a single joystick. Each thruster’s speed is continuously variable from full forward to full reverse thrust. The pilot’s other hand controls the up and down angle of the dive plains, which direct the thrust and provide hydrodynamic force if the sub has forward speed. By combining different thrust and angle combinations, very precise control is accomplished in all directions.

Fly-By-Wire Joystick

The thruster speed control joystick is actually a fly-by-wire system, somewhat similar to what is used in military aircraft. A computer actually reads the joystick position and applies the appropriate speed settings to each motor. Rather than directly change motor speed in relation to joystick position, however, the computer ensures that there is no harmful over-control of thruster speed variation.

Indicators on the control panel provide visual feedback to the pilot of each thruster’s speed and direction by varying the illumination intensity of color-coded directional arrows.

Electronic Buoyancy Control

Electronic buoyancy control is the true key to the success of the SportSub design. Without automatic buoyancy control, the pilot of an ambient pressure submersible would be too busy adjusting buoyancy to safely navigate and enjoy the dive experience. Dangerously fast descents and ascents could occur if the pilot ever lost control. The SportSub’s automatic buoyancy control system keeps buoyancy constant throughout a dive, regardless of depth.

The pilot initially sets neutral buoyancy manually, since it is different with each set of passengers because they have a different combined weight. Once neutral buoyancy is set, the system is switched to automatic and the electronic system takes over. As it senses compression, while the sub is descending, it adds air to the cockpit to maintain volume. When the sub is ascending it allows air to blow out of the cockpit rather than expand in volume. By maintaining a constant air pocket volume in the cockpit the sub’s buoyancy remains constant as pressure varies.

Automatic Depth Control System (standard on ResortSub and SurveillanceSub)

The new Auto Depth Control system uses 4 fixed position thrusters instead of the 2 variable position thrusters of standard subs. All 4 thrusters are computer controlled by a single joystick. There are three available modes of operation:

Manual Mode
Auto Hover Mode **
Auto Target Depth Mode **

** Includes Auto Ascent/Descent Rate Control

With Auto Depth Control engaged, whenever the vertical thrusters are not being operated manually, the computer takes control of the thrusters and uses them to hold the sub at its current depth. When the pilot wants to change depth, the thumb switch is used to ascend or descend. Once you have reached the depth you want, the pilot releases the thumb switch, and the computer again takes over and will maintain the new depth. Auto Rate Control is operational in this mode. With Auto Target engaged, the pilot uses the thumb switch to scroll to a target depth as indicated on a digital readout, then releases control. The sub will ascend or descend (as required, to attain the target depth) and will hold at the target depth once it is reached. Auto Rate Control is operational in this mode.

The Auto Rate Control function or 'automatic ascent rate control and descent rate control', helps prevent the sub from ascending or descending too quickly (faster than 1 foot per second). This is a significant safety feature.

This is a basic overview of the Auto Depth Control System.
For a more detailed description, click here.

Electrical Systems Monitoring

All the SportSub’s high current systems, from the battery to the thrusters, are monitored continuously by a computer. The computer detects any change in conductivity such as a short or open circuit or any unexpected change in resistance. It also monitors the temperature of critical components and causes the thruster motors to operate at reduced current draw until the components cool.

The computer also monitors the battery’s energy level. This provides a real indication to the pilot of the amount of charge left in the battery. It is far superior to a voltmeter because the voltage of a battery doesn’t change much until it is about to reach a state of complete discharge. By then it may be too late to take corrective action.

All of these monitored functions are displayed to the pilot on one simple multi-color, multi-segment LED read-out. Under normal operating conditions, the number and color of lighted segments indicates the percentage of charge remaining in the battery. If a single segment is blinking it’s an indication that a fault has been detected in the system. The operator refers to the owner’s manual to identify the fault.


Sonic Navigation And Ranging. This type of technology has been used in military submarines since their inception. In the early days SONAR systems were large and cumbersome. Their displays were subject to interpretation by highly trained and experienced operators.

Fortunately for us, modern electronics has miniaturized and taken the guess work out of these devices. In the SportSub a very sophisticated, miniaturized, SONAR system provides ranging that can be switched from measuring distance to an object in front of the sub to beneath the sub. The combination of these two ranging views provides valuable information for safe navigation. The system analyzes all sonic echoes to determine which might be false or multipath echoes. When a true range is determined the system locks on, then creates and maintains very accurate distance readings. Range information is displayed to the pilot in the form of a straightforward three-character digital readout.


The ReservAir system provides two essential emergency backup functions. It consists of a manual override for the electronic buoyancy control system and a completely redundant air supply to all the SportSub’s systems.

The ReservAir tank is located within the nose of the SportSub and its regulator and controls are completely separate from the main air supply. If the main air supply is depleted or has a malfunction of any kind, the ReservAir system provides enough air to safely continue the dive and bring the sub to the surface.

The other function of the system is the manual cockpit air inlet. This valve allows the pilot to adjust cockpit air volume manually in case of a failure of the electronic buoyancy control system.

Drop Weights

The primary objective in any emergency situation is to get the SportSub to the surface. Surfacing is normally accomplished by simply pointing the dive planes up and propelling the sub to the surface. If electrical systems have failed there are several ways to surface the sub by adding air to any of the ballast tanks, thereby increasing buoyancy. In the unlikely event that both air supply systems, and the electrical system, have failed, or been depleted, it is still possible to surface the sub.

A series of ten pound drop weights are located in the cockpit. The pilot can drop these out of the sub, one at a time, until the sub begins to ascend. As it is ascending the cockpit air volume will expand.

These drop weights can also be used as ballast trim bars if a payload heavier than the buoyancy range is required in the sub. For every trim bar removed from the sub, an additional ten pounds of payload can be carried.

Removable SCUBA

SportSubs are equipped with removable SCUBA sets that supply a mouthpiece regulator for each occupant. These provide two functions; an emergency escape system, and an excursion system.

Although there has never been a recorded case, it is theoretically possible for a SportSub to become somehow trapped under water or punctured in a way that prevents the hull from retaining the air that gives it buoyancy. If this should occur and the sub can’t be brought to the surface the occupants could still surface by removing the SCUBA sets and swimming out of the sub and up to the surface.

In a much less ominous scenario the SCUBA sets can be removed from the sub after it has landed on the bottom to allow trained divers to take an extravehicular excursion.


All of the above functionality in a simple shell of a hull is technically elegant but it must also look elegant. The combination of cockpit and hollow, bottomless, ballast tanks could be shaped in almost any way that can be imagined, as long as they have the required volume and positioning. The goal of the SportSub design team was to create a look that was unmistakably a submarine. The image most people have of a submarine is a military vessel that looks like a long tube with a round nose, a conning tower, tail planes, and dive planes. Since the SportSub is a miniature submarine we decided to create a kind of caricature look - almost a cartoon version of the real thing.

SportSubs are manufactured in different sizes and have been painted in many different colors, in fact they are available in any color a customer wants, but the shape is unmistakably a SportSub.

Hull Construction and Finishing

The SportSub hull is constructed of fiberglass. That statement in itself, however, doesn’t do justice to the technologies that are incorporated. Fiberglass is a generic term used to describe composite compounds of fiber reinforced plastic resins but there are a wide range of fibers, resins and construction techniques that can make one piece of fiberglass as different from another as tin is from titanium.

The SportSub hull is all hand laid using multiple layers of woven and biaxial roving. Every seam is stepped to a different width at each layer. All interior components are joined with a curved interface filled with a milled fiber composite to eliminate air pockets. These construction techniques are more expensive and time consuming than those used in most common fiberglass products but are necessary to create a durable hull that can be submerged repeatedly and withstand tropical sunlight for many years.

The SportSub is not simply finished with an outer layer of fiberglass gel-coat. It is sculpted and painted in much the same way as a hand built automobile. The paint is formulated to bond permanently to fiberglass yet withstand water immersion and continuous direct sunlight. It is harder and provides a better barrier to deterioration than gel-coat does, yet presents a smoother, more lustrous finish. Areas of the lower hull that come in contact with the sea floor are protected with heavy, dense polyethylene plates that can easily be replaced if they get too badly scarred or cut.


This information is subject to change without notice.

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