Jungle Cruise video:
An egg-shaped cam would be good to use for this. I think Dan Efren’s steam punk machine, recently added to the Flickr group, uses a mechanism like this.
In my experience, when a boat is making way it tends to go up and down fore and aft, bow to stern. Boats rock more side to side when they are drifting (dead in the water) and the hull turns parallel to the waves.