If you fall from high while riding a boat nothing happens upon landing. However when you dismount the boat it breaks immediately.
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The same thing happens with horses and pigs. (they get damaged)
Possibly related to MC-96583
I don't think this is a duplicate, because MC-96583 is about riding a horse downwards without falling.
This is about falling down with a horse/pig/boat from a distance.
In both cases the horse/pig/boat receives fall damage only when dismounting.
The point is that when you're riding something, fall damage accumulates and is applied only when you dismount.
Confirmed.