You could create a collision channel for just ships and have it block whatever you want (probably everything depending how your ocean is setup) in project settings → physics. Most collission stuff can be handled through the deatils of a mesh → physics → collission and setting up collission primitives for static meshes and a PhaT for skeletal. Make sure you have collisions setup for your mesh aka make sure when it hits omething it doesnt just no-clip/ghost through.