The sea hoarse series of submarines was built in the late 1970’s when I was in high school.  They were inspired by a movie “the Neptune factor” made in 1973.Being a youth I’ll describe the craft as I remember it. The sea horse’s were extremely small and built out of odds and ends I managed to scavenge.   The submarines only dove in a swimming pool.  The Submarine was supplied with air carried by a water hose from a paint air compressor.  The pool was unusual in that it was extremely deep, nine feet in the deep end.

This section was written well after the events so I apologize in advance for any inaccuracies that may exist.

I know there was a news paper article printed in the Tampa tribune in the mid 70’s about the boat (1974-1977) but I have not yet found it. I don’t have any pictures of this submarine

The Seahorse is a Semi-Dry submarine.  This means the occupant is wet from the neck down.
It incorporats the attributes of a Diving bell and submarine.

There are various types of privately owned submarines. (For more information see: Types of Privately Owned Subs)
Semi-Dry Submarines

Principals used

The Seahorse and all my future submarines use the principals demonstrated the following principals.

Diving bell

Like a diving bell these submarines use the pressure of the water keeps the air trapped inside the cabin.


Buoyancy is how much an object floats.  It is a function of weight and volume.  An object has neutral buoyancy if it doesn’t sink or float.  A submarine sinks or dives when it weighs more then amount of water the submarine displaces.   A submarine rises or surfaces when it weighs less then amount of water the submarine displaces.

How it works
Air was supplied to the cabin (A Styrofoam cooler with windows) from a paint compressor through a water hose.  The air was fed continuously.  The water level in the cabin remained constant.
Inside the cabin was a small Styrofoam block connected to a line. Buoyancy was controlled by raising or lowering the Styrofoam block.
To dive the submarine the block was allowed to float in the cabin.  To surface the block was pulled into the cabin.
The operator sat on a wooden board in a metal frame.  The frame connected the cabin to the ballast.
The ballast consisted of concrete blocks



How to dive and surface a submarine using a Styrofoam block

When the submarine was not occupied it floated high. The foam block is all the way in the water.  This maximizes volume and buoyancy


The foam block is all the way in the water.  This maximizes volume and buoyancy. The submarine floats.  If the sub is below water it will rise.


The foam block is half in/out of the water. 

Cabin volume is lower.  At this point the sub is neutral it does not sink or float.


The foam block is all the way in the water. 

Cabin volume is minimized.  At this point the sub is negative it will sink or stay on the bottom.


The original cabin was a Styrofoam cooler.  Holes were cut out and replaces with the lenses of old swimming masks hot glued in place.  The cabin had two port holes one on top and another in front.  After time the Styrofoam cooler was replaced with a 10 gallon fish tank.  The Cabin was connected to the frame using twisted wire.  During one dive the wire holding the cabin on came lose.  The cabin shot to the surface and the frame and operator were dragged to the bottom of the pool.


The frame of the seahorse was made out of an old bed canopy.  It was cut and connected using screws and wire. A rudder was made using plywood and connected controlled using foot peddles

Cement cinderblocks were used as ballast.

Subpages (1): Dive - SeaHorse