Since becoming certified in 1991 Maui has become my favorite diving destination. The weather is great all year round. Rarely have I encountered visibility less than 100 feet. The beach sites are plentiful and diverse with easy and access. The remote and offshore sites are serviced by many operators.
My favorite site is "Turtle Heaven" / "Five Caves" in Makena on the west side of Haleakela. This is a great shore dive (and usually the second dive of the Molokini boat excursions). The marine life is incredibly diverse. On a single tank dive in February I encountered numerous tropicals, turtles, two white tip reef sharks and a pair of humpback whales.
The critics pan Hawaii as a dive destination because of the lack of corals, but the abundant diversity in other marine life more than compensates. Although I prefer to take advantage of Maui's great beach diving I have listed a few of the Maui based operators below. Also visit the MauiNET for additional operator listings and other Maui information.
Maui noka oi
Ed Robinson's Diving Adventures
Extended Horizons - Scuba on Maui and Lanai
Three Routes Scuba Diviing