Do Dolphins Ever Sleep?

Why does a dinghy slid backward as we try to climb out? Why are cold seas green and warm seas blue? Why do barnacles attach themselves to boat hulls? When was the rudder invented? What have been the main steps in the evolution of sailboats? How does wind create waves? These are some of the questions asked about the sea, the sky, wind and weather, ships, sailing, navigation and the life aboard answered in Do Dolphins Ever Sleep?