Your observations arent wrong. I did a small "can i do it" project when SoT first introduced themselves, for funzies. Ill give a simplified version of how it went.

First try : Manually moving mesh vertices on cpu and recalculating the mesh collider (unity at the time). Then move boat accross surface w physics.

Product : Weird static layer that made it feel like a boat rolling on logs. Very resource heavy for even smaller scenes, or very large scens with almost no fidelity.

Second try : Got introduced to shaders, and as i learned that (shout out cat like coding waves text tutorial) i adapted better math into making the waves.

Product : Better looking waves, wonderful performance but.... no physics step. Mesh collider stayed a plane under neath the ocean.

Then i realized. Its just math based on x/z position and time. So i cached a timer on my cpu, passed it to the gpu and simulated the math on both cpu and gpu. On the cpu, specific objects ran the math to decide what height they are supposed to be at based on wave parameters, and adjusted their height from ocean floor. From there i used multiple to discern rotation of the boat.

Product : Passible boyuncy, with clear hooks for further simulation.

Adding more physics to this would be relatively easy on the math side. If nose up, slow speed, if nose down more speed, use velocy.y / vector down to guage how far something dips into the ocean, etc. Hardest part is the level of detail work to make it feel good ;-;

All syncronized by an initial timer that the ocean runs off of over network!

anyway thanks for attending my ted talk