That whirlpool in Japan, how powerful?

That whirlpool in Japan. Caused, according to a BBC presenter, by currents of water flowing at different speeds.

I had thought that as authoritative a source as Mythbusters had disproved the notion that a boat could be pulled under by a whirlpool, but the BBC reckoned that without aid from its engine, a boat seen passing over the whirlpool would be sucked down. I think they may have suggested to the sea bed itself.

Would a fishing boat crew have had anything to fear from that whirlpool.

It doesn’t look to me like there’s a significant downflow in the center of that.

That downward force would have to exceed the buoyancy of the vessel, no?

Or, the whirlpool would have to have such a speed that the force would push the water in the vortex out, making a “hole”, that a ship would “fall” into.

I doubt a raft would sink in that.

The whirlpool was impressive in size and neat to see but there was no “suction” apparent that would sink ships.

I think at the worst a boat would get caught in it and could not motor out.

Unpowered boats can certainly get caught in whirlpools. Being sucked under isn’t the problem. Losing control and hitting rocks or other hazards, that’s the problem.