What water did you keep them in on the way home? Was it ocean water?
Ocean water will foul within minutes to hours, depending on what's in it (plankton, contaminates, etc.). I can't tell you how many times I collected stuff, like shrimp, in Florida only to find it dead 20 minutes later when I got home. The best thing to do, albeit the biggest pain in the a-- is to bring synthetic water with you and acclimate everything to that water. It's a pain, but it works! Everything I collected with synthetic has lived, even coral and inverts. I would take jugs of it and keep it on the boat with a small airpump/airstone going.
Another thing we'd do is rig the livewell on the boat with baskets to keep small collected animals in. It wasn't ideal, but worked too.