Whirlpools that swallow ships don’t occur in the ocean.
However, eddies, or strong currents, can be one hundred miles across in certain parts of the ocean.
They do not suck anything down or push anything up at a speed that you would notice, and while they could overturn a small boat, they could not swallow a ship.
Perhaps the only thing comparable to the Maelstrom would be some very strong tidal currents.
Sometimes, when the wind and tide are just right, the tides east and west of Scotland collide in a splashy convergence of flow.
It is no threat to a large ship, but could overturn a cockleshell boat.
These are not whirlpools, but simply tidal currents trying desperately to get where they belong.
The original Maelstrom, also called the Moskenstrom, is a similar strong current running past the south end of the island of Moskenaes, one of the Lofoten Islands off the west coast of Norway, which is dangerous at certain states of wind and tide.
There are also little cyclonic atmospheric features over the ocean that can pull a little water up, which could damage a ship or small boat, but these are wind effects, not ocean effects.
