So I left Hawaii in April last year. As for Maui...expensive but there are easy dive sites that are shore dives and renting equipment is easy so long as you have your certification. Look at Meetup. I think you will find you will have a better experience. I did do a the boat dive to Molikini Crater and that is amazing.
On Kauai...the best shore dive is Koloa Landing, depth really doesn't get below 30ft...you can park literally up to the dive site. I have done at least 13 dives there. Plenty of reviews on it. If you are not experienced then don't do it without a guide but if you are a regular diver, this dive you don't need to go far from the entry to see amazing nudi branchs. And if you look in the coral closely you will find a dragon moray. It's literally a wall. There is a square cement anchor where you enter...I mean it's easy, as you swim from the shore just look down. There will be drop. Keep along the wall. Because this is in a cove, you rarely get get high waves. This is one of the few spots to dive all year. You may hear the whales here about that time but it's hit or miss.
If you pay for a guide it's around 110-140 for two dives. The water is relatively warm too.
I used fathom five for the tanks and weights but they do all the rentals. They have great service and will advise on shore dives.
Again, if you're novice or you just want the comfort of a guide please do so. The guided shore dive I did was nice and slow but I had to surface with everyone else even though i had plenty of air...
The big island I only did the Manta but I had the most amazing time. The crew was fantastic and they let you dive until you needed to surface. Mostly at 800 PSI.
You will enjoy it.
