Submersible Accidents - Entanglement Stories

Techdiver in June 1965 hooked its surface buoy line around a vertical escaprment at 400ft depth.  The sub could not move forward but reversing allowed the line to be cleared.  In this case, the 1/4 inch line could probably not have been broken by deballasting.  This buoy line was permanently removed from the vessel!

Shelf Diver had similar problems with towed surface buoys.  Several times this buoy line was tangled in surface structures and once the support ship.  They added a line cutter so the sub operator could disconnect the buoy line.

A tragic accident near Key West, Florida in 1973 took the lives of E C Link and A Stover.  The men, along with scientists A Menzies and R Meek who survived, where aboard the Johnson-Sea-Link (Sea Link) submersible when it became trapped in the wreckage of a scuttled destroyer 360 ft underwater.  An anti-snag framework had been added to the submersible and apparently this became clipped into a snap hook on a fishing net snagged in the shipwreck.  Strong currents thwarted efforts of divers in freeing the sub.  The water temperature was 40F and this contributed to the accident by impeding the action of Baralyme in absorbing carbon dioxide from the air.  The divers were in a separate, colder compartment from the scientists and although they added fresh oxygen the two men eventually lost conciousness and died of carbon monoxide poisoning.
 

In October 1969 near San Diego, California, the Lockheed Deep Quest sucked a 3/8 inch polypropelene line into its port impeller and became seriously fouled.  A Nekton submersible happened to be only a few hours away and agreed to come over to help.  The Nekton and crew were able to cut the line with a knife on a manipulator arm and both subs returned to the surface.  The Deep Quest was a pretty substantial vessel at 40ft long and 100,000lb displacement and she could have dropped batteries or other ballast to rapidly ascend and snap the line.  But smaller subs wouldn't always have that option.

The US Navy nuclear submersible NR-1 snagged a discarded fishing trawl line with its screw.  Similar to Deep Quest the crew could have dropped ballast to try to snap the line.  This option was discarded due to the risk of being trapped in an extreme nose up angle and suffering an automatic reactor shut down.  Instead over a period of three hours they sawed through the polypropelene line using the dull manipulator arm claw.  Sharp cutter blades were later added!
  
           NR-1

Accident Statistics

Collisions

Other Risks

Observations and Conclusion