Submersible Accidents - Collision Stories

On a very deep dive a US Navy bathysphere collided with an underwater cliff on a dive with Robert Ballard.  The lifting hull which is filled with buoyant kerosene, was punctured.  Some fuel was lost from the lifting chamber but enough remained to get the ship back to the surface.  The crew spent some anxious hours closely watching their ascent rate. Note: need to verify the details on this.
  
     Trieste II (#1)

In 1964, operating in shallow water and exposed to wave action, the Asherah struck an underwater object.  One forward, down-looking viewport was cracked but did not leak.  External guards were added.

Here's a bizarre one.  The Nekton Alpha and Nekton Beta with a surface ship were raising a sunken powerboat near Catalina Island, California in 1970.  They attached a line to an existing bowline on the boat and moved about 100 yards off to watch the lift.  When the powerboat was lifted almost to the surface the bowline broke and the boat glided shallowly and rapidly towards the Nekton Beta, with a steel skeg striking the conning tower of the submersible.  The impact shattered an observation port and dazed the pilot Rich Slater.  The Beta sank to the bottom and filled with water up to a level where the internal pressure matched the ocean pressure and in a semi-concious state Slater managed to swim to the surface.  He was luckily picked up and rushed to shore.  His copilot Larry Headlee was found dead on the bottom.  Slater survived with ruptured eardrums, cuts and a concussion.

In 1990 Carl Hardwicke died in a submersible  accident in a Michigan lake in 40ft of water.  Hardwicke, an engineer, had built the 8ft long, 3.5ton submersible named Sneaker 100, for pleasure use.  On the last of several test dives the acrylic nose dome broke open after apparently colliding with something on the bottom.  The other man aboard, Gregory Hansen, escaped through the shattered dome and made it to the surface with severe cuts to his head and body.  Speculation is that the boat may have hit a sunken log, many of which litter the bottom of this lake.  Material or manufacture problems would be other possible causes of the failure.

Accident Statistics

Entanglements

Other Risks

Observations and Conclusion