Jake wasn't crazy about going out in the rain. Ceasar's coat is so thick I don't think he ever notices rain. Dart would rather wait to do his business then go out in the rain. They all will go if I insist but Ceasar is the only one how doesn't act like it bothers him.
What all of them have despised is swimming. Spooky would "protect" us from the water, trying to keep us out of it by pushing us backward.
Jake would swim with me, but generally he would do his best to pull me to shore. One day I went out on the boat, and Jake stayed on the shore with my grandmother. He could see me from the shore and seemed fine. Then I jumped out of the boat to water ski, and he had a fit! He barked and jumped and was really upset. I'm sure he thought I needed rescuing.
Ceasar won't swim at all. In 10 years, he has only swam about 5 feet. One day we were hiking in a shallow creek. The water got deep enough he had to swim for a few feet to get where it was shallow again. It took my husband and I about 10 minutes to push, pull, and prod him through the water. Once he realized he was going to have to swim instead of walk, it was almost impossible to get him to move. I figured at worst we'd "carry" him in the water the few feet we had to go, but once we got his feet off the ground he swam. He wasn't happy about it, however.
Dart hasn't ever been swimming, yet so we shall see. He loves wading more then any of the others, so we will see this summer.
My experience has been that pyrs in general don't like water much. I guess mountain dogs don't have a lot of reason to go swimming.