It was so fun to see this pod of dolphins. I always wonder why they stay with the boat, it is almost like they are playing with us. Actually the dolphins are in sleep mode and that is why they can always find them on these tours. Here is a fun fact about dolphins: Dolphins have to be conscious to breath. This means that they cannot go into a full deep sleep, because then they would suffocate. Dolphins have "solved" that by letting one half of their brain sleep at a time. This has been determined by doing EEG studies on dolphins. Dolphins sleep about 8 hours day in this fashion.
A dolphin's behavior when sleeping/resting depends on the circumstances and possibly on individual preferences. They can either:1. swim slowly and surface every now and then for a breath 2. rest at the surface with their blowhole exposed 3. rest on the bottom (in shallow water) and rise to the surface every now and then to breath.