Columbia Shallows is by far, the best shallow dive on Coz., I call it an "aquarium dive" but it is a boat dive.
Cedral Wall & Santa Rosa Wall both have shallower sections for wall diving. In fact, you can pretty much go shallow on most dives if you want. I've many times stayed at 65' on wall dives when everyone else is at 80'+. As long as you let your DM know and stay with in eyesight of him/her.
San Clemente, Yucab, Francessa & Dalila are 4 of my favorite second boat dives.
There is a nice shore dive at Blue Angel around the Stingray enclosure next door and just beyond.
you can also do the entire drift from Blue Angel South (Hotel Villablanca area) up to Blue Angel Resort.
Also, if you can find a place to get in, going from say, Ernesto's Fajita Factory or just before that, drifting/moving north, is a VERY cool dive. Sort of a hidden secret, if you will. We did it a couple/few years ago, I just can't remember where exactly we entered, but we ended getting out near the Papa Hogs/Villablanca area (this was before Turquoise and Blue Angel South were there)
I've also heard that if you set it up, there is a DM at Playa Corona that will take you out on a shore dive off of there, that is very nice, but haven't personally done it.