North of Lahaina and Kapalua, the snorkeling at Mokuleia Bay is popular for the good coral on either side of bay. The Makulei'a Bay (aka Slaughter House) is part of the Honolua-Mokuleia Bay Marine Life Conservation District. It is also well known for its green sea turtles, parrotfish, humuhumunukunukuapua’a (Hawaiian state fish aka rectangular triggerfish), tangs and wrasse. The best snorkeling at Makuleia Bay is in the morning if there is calm water, however, there is usually a pretty good rolling surf coming in. If you can get past the line of breakers, don't expect to see much off this sandy coast -- the water clarity with surf on the sand is pretty poor. There is one small reef off the middle of the beach. The rocks to the right and left sides of the cove are not particularly interesting. Honestly, this is more of a boogie boarders beach; for a better snorkeling experience, try the adjacent Hololua Bay to the north.
To reach the snorkeling at Makulei'a Bay from Napili, head north on Highway 30 to milepost 32. Park completely off the road near the chainlink fence on the cliff; make sure you are outside the white sideline. There is a concrete staircase behind the green railing leading down to the beach. To reach the snorkeling on Maui by air, you will need to fly into Kahului Airport (OGG) which is located in the middle of the north coast of Maui. It is served by direct flights from the mainland US and also by inter-island flights from several other Hawaiian Islands by regional carriers.
Overall, Mokuleia Bay is the 9th most popular snorkel dive spot of all 21 snorkeling dives in Maui.