Realms -
Boats disappear after leaving.

Place boat in water. Board. Leave. Boat is missing. I can see the shadow where it was but I cannot see or break it.

In 2-player mode:
1) If the person operating the boat leaves, the passenger and boat disappear. When the passenger leaves the boat, they reappear to the other player. The passenger can see the boat, the first person cannot.

2) if the passenger leaves the boat first, they can see the boat and the other player. When the passenger breaks the boat, the other player can pick up the boat.