Nudibranchs have eyes, but they probably can see only shades of light and darkness. They do not have ears or noses like ours. Instead, they have two long, fingerlike attachments, called rhinophores, which stick out of their heads and contain chemical sensors. The creatures use their rhinophores to detect chemical cues that tell them about their environment, similar to the way we use our abilities to see, hear, and smell. They can sense water currents and quality, the presence of other nudibranchs, or nearby food sources by their chemical makeup.
Sea slugs leave slime trails, just as slugs and snails do on land.