system
Given the following post, respond as if you're commenting on Reddit:
human
How do fish and whales regulate their body heat? They have some mechanism analogous to sweating or panting?

If so, could they die if they're in too warm waters? For example, would an orca with a lot of blubber for colder waters die of something like a heat stroke if it started swimming rapidly in tropical waters?
gpt
Most all fishes are ectotherms (cold blooded) so their body temperatures are regulated by their surroundings. Some fishes like billfish and tuna, are poikilotherms, which is somewhere in the middle of cold and warm blooded.

Whales most often have to work to retain heat, since water removes heat much more efficiently than the air will. When in warmer waters they move blood into the fins and fluke, which act like radiators to dissipate heat. When they want to retain heat they restrict blood flow into the fins.