When using a boat on (packed) ice, and you press right/left arrow on your keyboard, you will start to spin uncontrollably. When you get out of the vehicle, it will stop spinning, but if you get back in, it will start spinning again.
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duplicates
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tomudding
migrated
Can confirm, movement of boat does not continue on player exit.
Edit: even if another entity is in it (villager, squid etc.) the boats velocity gets "paused"