Blue Lake is a spring-fed lake that is fed by several warm springs which keep its water surface temperature about 60 degrees F all year round.
Blue Lake is home to a decent population of bluegill and largemouth bass, as well as illegally introduced Tilapia. It is very popular with scuba divers due to the warm water, and on most weekends you'll share the water with them.
There are also several small adjacent ponds that also hold populations of small bluegill. Fish can be very wary here due to the heavy pressure from both divers and fishermen. Be careful not to stray too far up the inlet, as the land is US Air Force and near or part of a test range (you don't want to accidentally become a target to a practice attack from an unmanned drone do you?) :).