If a hamster were to go surfing (which they couldn't do in Hawaii because hamsters are illegal there) then they would be surfing on waves. Waves are created from several pulses at regular time intervals and they carry energy. A pulse is a single disturbance which carries energy through a medium or through space. If a hamster was surfing and the wave reached a boundary such as rocks, it would reflect off the boundary and it would be inverted. However if the wave were to reach a soft or flexible boundary it would reflect but not invert. The waves in water that hamsters surf on are known as transverse waves. If the surfing hamster saw a shark they would scream and create a sound wave which is a longitudinal wave. If the hamster fell off its board and ended up underwater they could still scream because sound can travel through air, water, wood and even steel. Hopefully if the hamster has a good center of gravity they will not fall off the board!