In June 1973, The Johnson Sea Link, a deep-sea submersible, went on a routine mission off the coast of Florida. The Sea Link quickly became entangled in the cables and debris of a sunken ship. Trapped 360 feet below the surface for over 30 hours, four crew members fought for survival, but only two would make it out alive. 

Sources:

ENTANGLEMENT OF THE SUBMERSIBLE JOHNSON SEA LINK WITH SUBMERGED WRECK AGE OFF KEY WEST, FLORIDA ON OR ABOUT 17 JUNE 1973 WITH LOSS OF LIFE Coast Guard Washington, D. C. 15 January 1975

The Miami News Fri, Jun 22, 1973 ·Page 4

The Orlando Sentinel Sat, Jun 23, 1973 ·Page 4

The Palm Beach Post Sat, Jun 23, 1973 ·Page 4

The Miami Herald Wed, Jun 20, 1973 ·Page 158

The Miami Herald Sat, Jun 23, 1973 ·Page 17

The Miami Herald Fri, Jun 22, 1973 ·Page 22

The Naples Daily News