My Favorite Place to Swim is Upper Bidwell Park near Chico, California. The Lava from Mount Lassen flowed down there and crystallized into large black rocks.

In the Summer the Rocks absorb sunshine and become too hot to sit on unless you splash some water on them from the Creek. The Place called Bear Hole (Diversion Dam) is the Best of the Easily Driven to Spots. However It Does take some crawling over the rocks to get in. Last time I was there, at AGE 62 it was more than I could do so I went swimming at Alligator Hole Instead. That one has a gentle beach to wade into the water. I saw a Duck and a string of Ducklings there. That Gave Me an Emotional Feeling of Being One With the Universe... Sunny Day, Trees, Lava Rocks, Ducks and ME... All One... 

Bear Hole, Chico Creek California

Another EPIC Swimming Place is the One Mile Recreation area. During the Depression of the 1930s the WPA built a Giant pool there out of concrete. They Built a Dam Across the Chico Creek and the pool is Very Very Long and Wide... One thing that is wonderful is the Park is open 24 hours a day. Swimming at Night is Special. 

One Mile Swimming Pool Chico Creek California

Butte Creek is wonderful for Tubing. It's a Wild Ride in the Spring with Snow Melt. 

I lived in Chico in 1973 and 1974 and then again for about 5 years in the late 1990s early 2000s... 

Link to Everything I've Written about Chico: https://gvan42.blogspot.com/search?q=Chico