We are going on Friday with Jim Abernethy on his liveaboard "Shearwater" which he is using for day trip goliath dives. There are 12 divers max (and we expect less than that on a weekday). It is an all-day trip (leave at 9 and back by 4-5) and he gives 3 dives with long surface intervals. We are going to rent steel 100s for this trip. You bring 2 tanks and he re-fills one on the boat during your second dive. They do fill nitrox on the boat. Boat has A/C, nice cabin, battery chargers, and, best of all, a hot cooked lunch by his chef. They pick whatever sites are hottest with the fish.
Cost is around $100 plus the air fill, plus whatever gear you need to rent. I think it is a fantastic deal for 3 deeper dives and everything else.
They are easily accessible from Singer Island. I would recommend you go to Dan Volker's site, sfdj.com, which can link you to special rates at the Hilton.
Also, having dove with them before, I can tell you that their service and their care for their divers is just incredible, at a level that I have rarely seen. This is one of the best dive ops anywhere.