Submersible Accidents - Conclusion

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.

Improvements
Standardized hatches, rescue and escape gear.  Failover breathing systems and temperature control.  External connectors for air, electrical power and communications would help rescuers.  Surface supplied aid is often critical.

Self rescue could give the most immediate help.  One approach is to carry an ROV on the exterior of a small submarine.   This has been done for many years; maybe first done on the Trieste II but probably best known is the Jason and Alvin duo operated bythe Woods Hole Oceanographic Institute and made famous by Robert Ballard's expeditions. 

An ROV allows inspection of the submarine exterior, most of which cannot be directly observed by the sub occupants.  Manipulator claws and cutters could be helpful in clearing or cutting lines or nets from the host submarine.  Visually checking the sub exterior seems very useful and could give information on gas and fluid leaks, general physical condition and obstructions and snags.

Cutting blades integrated into a sub-mounted manipulator arm should help with entanglement.  Shrouds around propellers, and cutting blades attached to shrouds and props can also help.

Sources:
AP article from early on the AS-28 accident...

Johnson Sea Link - PSUBS.ORG

Michigan homebuilt accident - PSUBS.ORG
       Sneaker 100

American Deep Submersible Operations, Will Forman, Best Publishing Co.
       Deep Quest, Nekton Beta, NR-1

Dark Waters: An insider's account of the NR-1
       NR-1

Manned Submersibles, Frank Busby

Photo credits:
U.S. Navy, Momsen lung: U.S. Navy, SEIE: U.S. Navy Chief Journalist David Rush,

Accident Statistics

Entanglements

Collisions

Other Risks