I was trying to navigate my large multiplayer boat through a narrow passageway between two landmasses. When the river got to it's narrowest point it bumped up against both sides of the river and started taking massive damage per frame, springing 7 leaks and sinking the boat in about 2 seconds. While I was haunting the wreckage of the boat, another player travelling back from the lunar islands came to the same passage. Despite my very clear warnings they attempted to do the same thing and met a similar fate. Then at some point a third person must have done the same thing because we found the wreckage of a third ship a few feet below both of our wrecks.
We put warning signs up.
1. Build a rowable/sailable boat in or around a narrow landmass (just barely narrow enough to block a boat. I'm not sure how you're gonna accomplish that but all the luck to you.) 2. Sail the boat through the passage.