This skill is about the aquatic aspect of life. With Biology, you can study and dissect underwater life; with Botany, you knows aquatic plantlife; with Animals, you may treat aquatic animals. Even with Technology and Engineering skills, this is your ability to work with machinery underwater and have it work properly without being damaged.
This skill is meant to enhance other skills, although on it's own it is the study of ocean currents and a general familiarity with water (including general locations of wildlife.)