Yes, this happens in multiplayer on DS.
I'd also like to add that it can cause your controls to freak out. For example, if I run across the deck of my boat and it randomly tosses me in the water, my player can get stuck in a falling animation - yet some time switching to swimming then back to falling. This happened to a couple of people on my DS just last night. If we made it back on to the boat, each time we jumped our character would do 360s (spin). Often times other players would report our positions in different spots than we were on our screens. We did figure out that aiming with a bow or crossbow fixed the issue. strange.
Just like mentioned above, taking baby steps while on the boat deck seemed to prevent you from being tossed.