For a beautiful sight, watch a nearly-full moon setting into the ocean, in a dark sky, with white moonlight reflected across the ocean towards you.
The only time you can see this, is 1-3 days before a full moon, at 1-3 hours before sunrise. Look in the western sky, at about the same position that the sun has been setting. On the day of a full moon, and in the next few days, the moon sets in daylight, and so you do not get the beautiful effect that you get by seeing it set in the dark, before sunrise, on the last few days before full moon.
A couple days before full moon, wake up 20 minutes before the time the moon is due to set, to get this view. You can find out the date of full moon, and the time of moonset and sunrise, from home before you leave, on the Internet, by going to http://aa.usno.navy.mil/data/docs/MoonPhase.php (for the date of full moon) and tohttp://aa.usno.navy.mil/data/docs/RS_OneDay.php (for the time of moonset on any date).
If you refuse to get up around 4 AM for the above spectacle, or if you are not on Maui at the right time just before full moon, then you can get a partial similar view by watching a first-quarter moon set into the ocean around midnight. Check the above Web sites for date of first quarter moon.
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Photo of Moonset on Maui
See the page of Things To Do In Maui for Haleakala, Lahaina, Lavender farm, aquarium, luaus, whale watching, snorkeling, tours, helicopters, horseback riding, dinner cruises, parasailing, fishing, biking, golf, beaches, kids and family fun, and more.