Regardless of the wood type, whenever you are riding a boat and approach the shoreline the boat will "disappear" as you unboard or crash into the shoreline (EDIT: I should add that this happens not 100% of the time, but does happen often). This happens even if something is in the boat as well (i.e. villager, alpaca, etc.) The only fix for the time being is walking away from render/POV distance and coming back or relogging.

This issue happens for everyone on the Realm server. What I personally have noticed, when an alpaca was in the boat with me and the bug occurred. I noticed the alpaca was "teleporting" from the direction of where I departed (boat not included).