Boat sinking system with custom water (not terrain)

im trying to figure out a way to make a boat sink on flat part water (just a part mede to look like water)

i already made the boat float and stay upright by using 4 points and figuring out the rotation and position from there then using align position and orientation
but i cant find anything on sinking a boat

idea i thought:
adding an align position to each part that is used to calculate the position and rotation of the boat, and when its sinking move it down by some amount. this will give me the sinking but has a few flaws like i cant control the amount of hulls the boat has

remember this is not terrain water. the water has no collision or buoyancy
i know when using terrain water you could change the density of each hull to make it feel like the boat is sinking and falling down in the front because it has more water. but i dont know how to replicate that with custom water

anybody got any ideas?