WHERE: Turtle rock cleaning station, Wai'anae.

WHY GO: Hawai'i's green sea turtles love a clean house. To keep their shells free of algae — which can slow them down — Island turtle communities establish "cleaning stations." An underwater rock or a coral head serves the purpose ... or any place that shelters marine house cleaners such as damselfish, angelfish and other algae eaters.

One such station is offshore from Wai'anae Boat Harbor, where a large rock about 15 feet below the surface offers a prime cleaning service.

Turtles small and large wait to present themselves to the fish for a picking-over. The fish are hungry and the turtles are patient, circling and hovering over the rock until their turn. When their shells are clean, they move gracefully away.

Snorkelers in the area can observe this ancient ritual by also waiting patiently. Turtles will come and go calmly if undisturbed, allowing the experience to continue only if they don't feel threatened. And while waiting, you'll most likely see a pod of spinner dolphins shoot by.

Bring sunscreen and a disposable underwater camera — Kodak's Sport 411 works well ($10.99 at Longs Drugs).

IF YOU GO: Morning cruises for snorkeling and dolphin sightings leave Wai'anae Boat Harbor and Ko Olina Marina daily.

Wild Side Specialty Tours offer a morning cruise for $105, sailhawaii.com; Snorkel Bob's dolphin excursion is $105, snorkelbobs.com; Ocean Joy Cruises' early cruise is $99, www.oceanjoy.com.

Cruises include roundtrip transportation from Waikiki hotels, refreshments and use of snorkeling equipment.

If you're driving from Honolulu, take H-1 west to Farrington Highway. Wai'anae Harbor is at 85-371 Farrington Highway, opposite Wai'anae Intermediate School. Allow time to get there. Early-morning traffic is heavy and the harbor is not well signed. Park in the area to the right of the harbor entrance or your car may get towed. Note: Tours leave promptly and will not wait for latecomers.