Decreasing speed of waves as water becomes shallow has dramatic consequences on the beach. As the waves slow, their profile (Figure on right) is laterally compressed and since each wave must carry the same energy it becomes higher. As the wave approaches shore this process continues until the height exceeds 1/7 th the wave length and the wave becomes unstable. Then the wave breaks.
The horizontal movement of the water when a wave passes is approximately equal to the up and down movement of the water. If you are on flat water and are parallel to waves made by a passing boat, your boat will move side-to-side as much as up-and–down as the wave passes under you. The side-to-side movement actually creates most of the difficulty in balancing the boat in such a situation. However, under typical conditions in the bay there can be such varied wave action that you can’t easily distinguish horizontal and vertical motion.
In sweep or sweep-oar rowing, each rower has one oar, held with both hands. This is generally done in pairs, fours, and eights. In some regions of the world, each rower in a sweep boat is referred to either as port or starboard, depending on which side of the boat the rower's oar extends to. In other regions, the port side is referred to as stroke side, and the starboard side as bow side; this applies even if the stroke oarsman is rowing on bow side and/or the bow oarsman on stroke side.