I agree with using a local guide, Shaka Doug being one. I wanted an UW photographer, so I took Halemano.
Turns out Halemano is also a great guide. Should have listened to him more before heading out to Maui; we would have done one less boat dive, awesome shore dives, and would have saved money.
The not-so-great boat dive, that ended being a great shore dive from the boat, was the trip out to Molokini. In my opinion, not worth it. Even if you leave the dock at 06:30 am, other boats arrive with snorkelers in no time. There's more fish hanging around the boats than there are around the reefs.
Cathedrals 1 & 2 (lava tubes) where wonderful, it's a 1hr trip from Maala Ramp in Lahaina to Lanai island.
IMO, shore diving it the best bang for the buck for Maui. A guide is essential for knowing where the swells & currents are.
Like looking on a map, you would think shore diving at Honomanu Park‎ (North, East of Paia, road to Hana) would be great.
I'm sure the local guides of Maui would beg to differ.
Shore diving w/o a guide - try Little Beach and Big Beach. However, it's a good long walk with gear. Easier to snorkel those beaches.