If you don't have your own snorkel equipment, your hotel or resort may provide gear. If not, you can rent some; fees vary by shop and rental period. Popular locations include Snorkel Bob's ...
In fact, many of the island's top hotels will offer guests complimentary use of snorkeling equipment; some, such as The Ritz-Carlton Maui, Kapalua, will even arrange boat tours for their guests.
I used my metal detector and scuba gear to find all the treasure that laid hidden underwater at this busy water slide on the river. The best part was when I got the stuff returned to the owners!