Actually, the way you explained it seems fine, but have you checked out the tutorial in the help that I told you about?

If you open the help by typing F1 while in Maya, then browse to:

Using Maya > Dynamics and Effects > Fluid Effects > Open Water Effects > Create an Interactive Boat Simulation

This is the tutorial I told you about in the 3rd post

It tells you about the different types of locators to attach your boat to so it reacts better to the waves of the ocean in the way you need it to

Let me know if you tried that or not, and how it helped.