Boats are still being worked on but are still buggy. One of the bugs is they like to vanish when somebody enters them, this happens with vehicles too but its not as common (Boats tend to vanish once every 4 tries, vehicles do it rarely). Unfortunately due to them being invisible, they like to crash any players nearby when the player exits the boat so it needs fixing before we re-enable them.
Ah I completely understand, I've experienced this anomaly with cars about 5 times in several weeks where they will appear on the radar but I can't see them, and if I attempt to go up to the invisible car (based on their position on the radar) it does indeed crash me.