This is a maelstrom (Dutch “grind-stream”), whirlpool, tumult, pandemonium,
bedlam.  It formed when slower/warmer water interacted with colder faster water
near the reef wall, growing to 20’ in diameter, enough to swallow a 100’+ foot boat
and grinding hundreds of  fish down to ~30’ during its 30-45 minutes of existence.
The currents were very strong, requiring divers to seize coral and rocks as they
viewed the funnel spiraling up to the surface with an enormous drainage-siphoning sound;

“a toilet flushing at concert levels.”