Why so complicated? There could be many 'mini-labs' in underwater caves, accidental discovery of inverse diving bell so to speak. With trapped gases of any sort

Why so complicated? There could be many 'mini-labs' in underwater caves, accidental discovery of inverse diving bell so to speak. With trapped gases of any sort, by whichever process(volcanism?) pushing the water out downwards, while unable to escape upwards. Ready to explore, and mess around with. Maybe even in something like free floating coral reefs. Or below the ice.