Air tanks. Nobody dives on oxygen, it will kill you. It’s a common misconception. That said there may have been a bank of O2 bottles on board to mix enriched air (also known as Nitrox).
Truth Aquatics banks EAN32, so no need for O2 bottles except for First Aid bottles.
Last time I chartered the Conception, those who signed up for the trip and wanted 32 or 34 EAN paid in advance. Bottles were mixed at the shop and delivered to the boat. There are small O2 bottles for First Aid but no O2 other than that. There is some gasoline for the chase boats but that's about it for flammables -
The pictures look to be like the heart of the fire was in the berthing compartment - below the main deck on this boat there's 30 bunks and 4 stateroom style cabins. Its a very nice boat. Spotless and ultra professional.
Nitrox-yes, so advertised.