Using this float rig, Doug Ulmer shot an estimated 200+ pound tuna at Roca Partida. The fish took off like a rocket and towed the float down at a 45 degree angle. It disappeared into the depths. Water visibility was about 90 feet and the maximum depth around the rock was only 275 feet. Twenty five minutes later the float was spotted with binoculars from the Ambar III, a quarter of a mile away. They called to the Panga, the float's position and when it and rig was recovered there was no fish. The spearpoint and shaft were intact and the float had "disintegrated".

I had fabricated the float from a windsurfer board blank made of polyurethane foam of density 3.7 lb./cu. ft. The tested (after failure) compression strength on that foam is about 60-80 psi. The float was glassed with polyester resin and 2 layers of 16 oz. "aircraft" glass. The rails were double glassed and all stainless steel fittings were isolated from the foam by microballoon castings.

The trailing line on the "breakaway" rig consisted of 50' (bungee) compliance line which contained 100' of parachute cord. This was attached to another 50' Riffe brand non-compliance floating line. The shooting line was 35' of 400-lb. monofilament attached to a five and a half foot spearshaft. The whole rig when completely stretched out was no more than 200' long. The buoyancy of the float was previously tested to be 85 pounds.

The diver, Doug Ulmer, lost sight of the intact float when it was around 90 feet deep.  In estimating the trajectory and water depth, the tuna, at the bottom was never deeper than 300 feet. The float probably imploded between 120' and 150' depth.

Still, the collapse failure of the float was probably not what "lost" the fish.  Most likely, the fish was lost when the tip pulled out under heavy load. Clearly the float failed because the compression strength of the foam core was not strong enough to resist the pressure of the water at the depth the tuna took the float. The strong glass job did not save the core from collapse. This float still weighs about 30 lb.  Many cells in the polyurethane foam became permanently filled with seawater.

Current thinking among big game offshore spearfishermen is that Divinycel brand polyvinyl foam should be used for floats as it has relatively high compression resistance.  Density should be selected to resist compression to the depth the float may be taken down.

Choice of floats and float materials for hunting big game should not be based upon convienence or cost.  This was a hard lesson to learn.  As you can see from Doug Ulmer's face.