david, air and water are very different. first of all, water has a lot higher specific heat capacity meaning temperature will not change nearly as quickly as air and land do. that is why when you go swimming late at night after the sun has been long gone and the air is cold, the water will still be warm. also, i was more referring to water in a certain area, especially down along the equator where most of these animals reside. given the water around boston will change temperature with season, along the equator there is only 1 season really, that being summer. also suppose you were in a bath tub and you started the temperature at 70 degrees and slowly over a couple hours increased the temperature to 100 degrees. you'd be fine. now suppose you heated it to 100 degrees and then you jumped right in. i bet you'd feel the burn. fish, in the wild, never deal with instant temperature changes of even 1 degree so even 1 degree could be a bit shocking to them.