All vessels are subject to the Rules of the Road. A simple rule for two dissimilar vessels is that the more maneuverable vessel, a powerboat, must give way. However, when you consider how many different types of boats there are and how many different situations you will encounter, the rules are not always so simple. For example, when two powerboats approach each other at an angle, the vessel on the port side slows down and passes behind the other.
There are rules for every situation on the water. The basic ones and the ones most often used by pleasure craft can be found in the Safe Boating Guide.