Touch

Cetacean skin has many nerve endings sensitive to pressure that are probably responsible for changing the wrinkle patterns. They also have pressure sensing nerves around the blowhole.  Many dolphins have large numbers of sensory cells at the tip of the lower jaw.    Humpbacks have groups of sensory cells around the base of hairs in the nodules on their rostrums. And of course there are many sensory nerves around whiskers on a variety of marine mammals. All marine mammals probably have the typical vertebrate sensory nerves (touch, pressure, heat, cold).