Resentful straight sailors bemoan
That lesbian shipmates are prone
To choose delta patrol,
Where the action, on the whole,
Takes place in the littoral zone.
Delta, of course, is the fourth letter in the Greek alphabet, which later became the Latin “D” character. Since the triangular intersection where a river dumps silt and fresh water into the sea is so shaped, it is called a “delta.” See image above. The joke here is that the mons veneris — the female pubic mound — also sports a triangular patch of hair. Littoral is a fancy term for the area on or near the shore, where, apparently, it’s not just the captain going down anymore. It’s funny because it rhymes with “clittoral.”