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Sub-Log survey

To be completed...

Equipment Failures
Diving Saucer (SP-350) in 1959 suffered a battery short-circuit.  The standard ascent weight was dropped and the sub ascended until gas in the battery box exploded.  The sub began descending, an emergency weight was dropped and the sub surfaced.

In 1966, DeepJeep accidentally dropped its electromagnetically secured ballast plates.  The sub began ascending to the surface where 5 or 6 ships were operating.  The operator somehow (water ballast?) stopped the ascent at 30ft.

Natural Conditions
Abrupt water density changes can affect buoyancy trim, for example when moving from salt to fresh water.

Undersea currents can overwelm the propulsion and control of small submarines.  Currents may run several knots or more.  The NR-1 encountered very strong "tidal wave" like currents which struck the boat periodically on the bottom of the Atlantic.  The crew was later able to estimate the schedule of these undersea waves and prepare for them by trimming the boat heavy and sitting on the bottom to ride them out.

Observations
Escape devices have been carried onboard large submarines for decades.  Devices such as the Momsen Lung, Steinke hood, or the latest Submarine Escape Immersion Equipment (SEIE) help a sailor breathe, and hopefully safely ascend and survive on the surface. 

        
     Momsen Lung                 SEIE

The new SEIE is supposed to be good to depths of 600ft but since many submersibles are deep diving this severely limits the chances for escaping from a trapped vessel and doing a free ascent.

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.

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 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.