The ocean, like the atmosphere, is not isolated. It swims, and is affected by pushing and bumping air, and pushing and bumping water that creates swirling. Just imagine the Earth's air and water currents with a great deal more turmoil - cold water rushing in, the sloshing that occurs when the Earth is turning under the water so that great tides occur, and then a reversal, a pulling back, as water finds its level. Humans are used to thinking of slow moving rivers and tides that ease in and ease out. Imagine if the press behind the water is strong and the waters move rapidly and crash, bore up into the hillsides because they have no place else to go, swarm over the countryside beyond the hills that might bridge along a coastline and come roaring back out to sea so that people find water coming from behind them, coming from inland and from the ocean alike.
Water can be very unpredictable, although it can be analyzed if one sits and thinks about it a bit.
A boat is not a safe place during the coming pole shift, unless one is prepared to be in the middle of an ocean, or washed well inland, or floating upside down, or drawn down into a vortex such that they are underwater for an extended period of time.