Nab Tower is a boat-access Solent dive around a historic anti-submarine tower that now marks the deep-water eastern entry into the channel. The structure and nearby rock hold crabs, lobsters, wrasse, bib, blennies, gobies, and cat-sharks, with the best viewing on the upper and mid-water parts of the tower. It suits divers who are comfortable with tidal timing, drift-style pickups, and an active navigation environment rather than a sheltered reef.