I've tested boats on my custom map and there is a problem with water particles position.
My map is built above the 0 meters ocean level and all water bodies are made of river/lake parts used for example on Livonia.

And the problem is that particles from the boat are positioned at the ocean level. They follow the boat and its rotation angle, but not the height on the map.

On first image I clipped the camera through the ground (between 110-120meters above 0 level) and you can see that the boat lies on the island and particles are beneath the surface.
On the second image I teleported outside the map frame where I can see the ocean level and its visible here that there is a problem with position.