Kapalua
The best bay snorkeling on Maui — an almost-enclosed bay with no beach runoff, exceptional water clarity, dense coral, and extraordinary fish diversity. The forest trail through the old plantation gives the feeling of discovering somewhere secret. Go as early as possible: morning glassy conditions give 15–20m visibility; afternoon trade wind chop degrades it significantly. Note that the entire character of this place changes in winter: November through March Honolua becomes one of Maui's premier big-wave surf breaks — snorkeling is impossible and the surfing from the cliff above is spectacular to watch. Check conditions before driving up.
Free, no reservation. Parking on Hwy 30 at the bay pullout, 4 miles north of Kapalua — small gravel lot, fills quickly. Walk 5 min through a former pineapple plantation forest to the pebble beach. No facilities on-site; gear rental from shops in Kapalua or Lahaina. The bay is a State Marine Life Conservation District — nothing can be taken.
Summer (April–October): snorkeling. Go in the morning for best visibility. Winter (November–March): big-wave surf break — watch from the cliffs, do not enter the water under any circumstances.