I wouln't say it's better or worse - just different. You're not going to see the soft fans/corals like Bonaire but the fish life is pretty plentiful at some locations. I have non-stop access to Hawaii so have been there a lot more times than Bonaire. Another difference is that since Maui is volcanic, I often read posts that claim it's barren. It's not but you have to slow down/look harder sometimes. Hawaii has one of the highest endemic species counts in the world so they're out there. You often see schools of tangs/butterflies etc in relatively shallow water. Not a lot of the Maui shore dives get very deep - 70' or so is about all unless you swim out - or rent a scooter. So a lot of the better diving is 30-40' - at some sites nothing much exceeds that. Lots of turtles - part of the West Maui coast is called "Turtle Town" - which encompasses several boat/shore dives and you regularly see reef sharks. Turtles also bring TIgers into Olawalu on occasion - I've yet to (but hope to) see any.
Most of the entries are pretty easy. Almost all are beaches - there's a few where you pick your way over the lava but it's been ground down by waves in most places along the waterline. Once you're in the water it's usually pretty easy going - often a sandy bottom leading to coral starting deeper than you can stand. I've never even thought until now about the entries, they're so benign. One exception - and a good dive - is Mala Pier in Lahaina. The legal entry requires picking through the coral out to deeper water - the illegal entry is easier but across an active boat channel. If there's a DLNR agent nearby - you will get a ticket. Also they're going to want to see you enter and leave with a flag at all the sites - the shops rent them. It's been my experience that they're more active in South Maui - I've seen an agent there once or twice watching divers with binoculars.
There's very few resorts with dive operators on site unlike Bonaire. It's because the big hotels/condo complexes are on the best beaches - not the best dive sites. The few that do have one aren't on good dive locations. Two exceptions might be the Sheraton Black Rock and the Wailea Grand - both are on named shore dives. Each has a dive operation for guests but not external customers.
Multiple Maui Dive Shops in both West and South Maui rent tanks, sell fill cards etc. So do most of the boat dive operators and there's also a couple of shore dive operations - two I know are Maui Dreams Dive Co. in Kihei and Tiny Bubbles in Lahaina - there' about a dozen others also. And freelance guides who generally meet you at a location, Shaka Doug/Shaka Divers is one in the Kihei area and I also know Scuba Mike who I believe works the whole coast line. It's often recommended to hire a guide first as they show you how to find the good stuff. After a couple dives though you start to figure it out. One tip is that many of the beaches are typically more rocky at either end - if you go in off the beach in the middle it's a longer swim to deeper reef - if you go towards the point you run into reef, lava tubes, overhangs, caves - sometimes as shallow as 30-40 - esp. in South Maui. Sometimes one point is a lot better than the other also.
If I was going to do a lot of shore diving - I'd base there. There must be almost a dozen good dives within 10mins. of Kihei heading south into Wailea. The West Maui sites are more spread out but worth a drive up a couple days.
For boat dives a general rule of thumb is the Kihei boats go to Molokini Crater and the Lahaina boats go to Lana'i. Some do both. The reason is that Kihei boats are trailered in and launch from the ramp, boats in Lahaina harbor - or Ma'alea harbor farther south - are moored at the docks. The tradewinds pick up in the early afternoons making the return from Molokini rougher so the smaller obats leave early (5:30-6:30) to get there and back b4 they do. 2nd dives with anyone are often along the Maui shore line also.
Boat traffic isn't really an issue since except for Mala Pier there's no dive site near one. You have to watch for sailboats off Kihei if you surface in deep water but you likely won't Most of the better diving off Maui really doen't exceed 70' - at some the reef would tear up any boat that tried to enter the bay also. Jet skis are a different issue but one of the rentals is off Ka'anapali Beach and there's no good diving there.
All the beaches - and dive sites - are public. Even ones with resorts on them have to provide public access. Often just a path so you drop your gear and someone goes to park. The lots fill up fast in the mornings - we've circled 15-20mins. waiting for someone to leave. Lunchtime is a good time to find a spot and we've never had any problems on afternoon dives. Some of the more popular beach sites also have big lots so it's never an issue.
Many dives are also really nice beaches so if you have non-divers they may want to go along - Kapalua Beach for example is one of the nicer ones in NW Maui and a decent - but shallow dive.
Here's the shore dive list. As you can see predominantly they're near Kihei/Wailea. My top 5 dives on the list are Makena Landing, Polo, Ulua, Wailea Beaches and Old Airport. Not included but one of the best is Mala Pier in Lahaina. Some of the farther north sites are long carries or rougher entries and weather dependent - you can't tell until you get down to the water though sometimes. Watch the surf reports - if they're reporting good in an area the diving will typically suck.
Scuba Shore Diving Site Listing for: Maui, Hawaiian Islands
Maui Ocean Center also has a dive with the sharks exhibit. Tell your friends you went to Maui and dove with a Tiger shark. (he's about 3' long...) If you plan your trip during Humpback season - mid Dec. to March? - you'll hear them singing off Molokini. And often see them on the ride over - or on a whale watch cruise.
