Divers don’t use 100% O2 in their tanks. At most the tanks would be filled with 32% O2 compared with the 21% O2 that is normal compressed air.
It is very difficult to make a scuba tank explode. Normally, if the tank is heated and the pressure inside rises, as in a fire or even in the trunk of a car on a hot day, a burst disc in the tank valve will rupture and release all the air in the tank very rapidly. An exploding tank usually occurs when the tank has physical damage or is filled incorrectly.
And I’m a 30 year scuba instructor who has inspected, serviced, and filled thousands of tanks. The diver’s tanks in this tragic accident are only an incidental consideration.
I think something on the boat went up really quick. The suggestion of a galley fire accelerated by the fuel for the galley stove may not be far-fetched.
Thanks!