Why fish can maintain fairly active lifestyles, even in low water temperature, while terrestrial ectotherms typically function on a narrow thermal range, and even then, most can afford mostly slow and sit and wait or move and pause for much time lifestyles? Also, why most teleosts are constantly moving, while more “primitive”, lunged  species are ambush predators like Mmost amphibians and many reptiles?

sorry no-one seems to know the answer to your question.