Boats on the Minecraft client get off sync in short periods of lagg. This accumulates over time and will most certainly lead to the server boat crashing into a beach which seemed to be far away on the client side, which is very annoying.
Instead of waiting for this effect to accumulate over time, once your boat is displaced by a few blocks, you can also get the client boat stranded on a beach while the server side boat is free to move. This way driving the boat against the beach results in the boat on the server side moving, the client boat still stuck on the beach.

Steps to reproduce:
1. Join a server which runs on another machine.
2. Get into a boat
3. Plug out your network cable to simulate lagg.
4. With the network cable still plugged out start moving the boat.
5. Plug in the network cable before your client disconnects.
Now your boat is displaced a few blocks on the client side

Attached screenshots:
1. boat on server side running away while stuck on beach client side. I'm towing a donkey behind, so you can see the actual position of the boat.
2. leaving the boat will leave the player wherever the boat is server side. The client side boat still is off-sync somwhere else in the background.
3. After relogging the boat appears where it really is.