Three short lines, and almost everything in them is left unsaid. The speaker begins with a confession, "I couldn't help it," but never tells us what "it" is. That gap is the heart of the poem. It sounds like someone excusing themselves, as if they gave in to an urge or a mistake and can't fully explain it.
The next line, "Living by the sea," offers a setting, and maybe a kind of reason. The sea can suggest freedom, restlessness, or something bigger than the person standing beside it. Then comes the odd, vivid image of "manic toes" knee deep. Toes can't really be knee deep, so the picture feels slightly off, as though the body has taken over and is acting on its own energy.
The mood is playful but uneasy: restless, impulsive, a little breathless. The title, "REF II," hints at a series or reference point, but the poem itself doesn't explain it, so the meaning stays open for the reader to fill in.