2 Answers

Oh, but dolphins and whales CAN get decompression sickness. Here’s a bit I C&P’d:  

Whales, seals and dolphins all posses similar adaptations that prevent them from suffering decompression sickness as they go about their daily activities, but despite these, marine mammals have been seen with symptoms that could indicate decompression sickness. Many stranded animals have been found to have legions (tears) in their tissue that may indicate damage due to bubble formation. Determining whether or not decompression is the cause of this abnormal tissue is a difficult process as the tissues need to be studied soon after an animal has stranded, otherwise, we can't distinguish between damage due to decompression from that due to decomposition. To achieve this, the stranding has to be reported by a passer by almost immediately after the event and marine biologists need to be dispatched to take a closer look at the stranded animal ASAP - no easy task!