Dive computers are not included. Wet suits are not needed. Hubby used to pack his shorty but now just dives in a t-shirt and shorts. He only bring his own snorkel, mask, boots and fins. The rest he uses what they have. (They also have fins, masks and snorkels though).
As Amy said they have everything you need, but you'll probably be happiest with your mask, snorkel, and fins at a minimum. You don't need a wetsuit or gloves, but you may want a dive skin to protect against rash/jelly fish. If you have all your own gear and you have the room I say bring it, the more experienced divers definitely bring their own BCD and regulator setup.
We always bring our own masks, snorkel, and dive skins. We have done their or ours for fins but I prefer mine since we normally wear booties. No computers are provided or needed. None of the dives are long enough to worry about. Wetsuits are not needed either but I do recommend a full body dive skin. I had a HORRIBLE reaction to the jelly fish eggs one year and never dive without a skin now.
we rented the dive skins for 10 each dive at cti. We also took our own mask and snorkel so that we could snorkel from the beach and the cat cruise. We saw star fish, sea urchins and a little spotted ray. My husband took his computer, bcd, and fins as well. I used the gear there and it was not that bad in my opinion but I am new and used to rental gear because I have not gotten my own yet.
Wetsuit is unecessary....the water is plenty warm and you aren't on a long enough dive to get "cold".
If you fear reef rash/jelly fish a dive skin is nice added protection, but certainly not necessary. My wife wears one when diving @ CSA, but I do not. They typically cost ~$50, so the question is the peace of mind from jellies worth $50 to you?