What I expected to happen was...:
The tammed wolf to teleport to me.
What actually happened was...:
The wolf repeatedly attempted to teleport to me but was returned to the boat each time.
Steps to Reproduce:
Pick up a swimming tammed wolf while sailing a boat, leave the boat and move far enough away for the wolf to attempt teleport.
Mod Edit: this can occur with any vehicle entity (i.e. both boats and minecarts), and affects teleportation by endermen in addition to wolves.