I've got a Sealife DC310 and it's shutter delay (or lack of) is pretty decent. (in my opinion). They have replaced that camera though with a new model called the DC500, which they say has "shark mode" for fast no shutter delay of up to I think 3 pics.
However, the Sealife cameras have their downside (in many peoples opinion, not just mine). My problem with the DC310 is that I often get a "white burn" from the auto white balance not working as well as it should.
The DC500 has had all kinds of fun problems. Mostly firmware/software related, but also the same white balance problems. One of the things I don't like about the DC500 is the proprietary battery system. Example is that this week on dive 1 of the day my batteries were low. On my camera (which uses AA's) I simply switched batteries between dives. That's harder to do on the DC500 as you have to buy a 2nd proprietary battery system for a spare battery. If you want to charge it seperate from your camera, you have to buy a seperate charger system also. Then you still have to buy AA rechargeable system for the strobe, so now you have to have to battery/charger systems for one camera. Too much of a pain in the rear.
Now... on to the Sea&Sea. I've never used one of these but a coworker just came back from a trip and one of their complaints was the shutter lag on their new SEA&SEA camera and how many "missed" pictures they got because of the shutter lag.