Lithium battery charging and overcharging. People shoot pictures nowadays instead of fish. I’ve used Conception before. It is the jewel of the California dive boat fleet. A multiple lithium battery explosion and fire directly above the berthing compartment where 34 people were asleep is something we haven’t seen before. This is speculation. Also, on multi day trips, many times emergency hatches get blocked with gear bags, clothing bags, dive tanks, scooters, cameras etc etc
Bingo.