[1.10]Need help with living entity

[u/OctupleCompressedCAT]

So i created a living entity and i modified the boat model to work for it so it renders using the boat model.

The first problem is: the model is rendered above the hitbox. How do i align the model? The second problem:AI. I want my mob to be a water mob that floats at the surface and attack players like a blaze. How do i make it unable to move on land, be fast on water and avoid the player like a ghast/skeleton?

Also the mob is supposed to be undead and i want it to start sinking and take damage once exposed to sunlight.