I have been keeping a small tidepool tank all of my life (I'm old)
I am in Long Island in NY and we have many tidepools. I have a boat so many of the tidepools are available to me that are inacessable to others.
Virtually all of the animals in tidepools will live without a chiller because as was already stated the water normally goes over 90 degrees in shallow pools.
The only local animal I can't keep in an unchilled tank are local hermit crabs and horseshoe crabs which will only live a couple of weeks. But the shrimp, green crabs, fiddler crabs, Japanese shore crabs, blue crabs, rock crabs, snails, worms amphipods, barnacles and many fish will live forever. I use no light or filtration and just a small powerhead for agitation. When I change my tropical reef water I use this old water to change the local tank water.
I throw in some pellets every few days.
It is very interesting to watch.
Yesterday I collected some eggs, I have no Idea what they are from but I look everyday to see if I can see something new swimming around.
Have a great day.
Paul