Deception Pass State Park is primarily known for its beaches, but Cranberry Lake is an important addition to the park. It's much warmer than the adjacent West Beach (on the Pacific Ocean), which makes it ideal for a dip in summer. The western shore of the lake has a designated swim area and restrooms. You may find a curious otter swimming alongside you. The east side of the lake is more geared toward fishing and boating. Only human-powered or electric motor boats are allowed in the lake, which in theory makes the lake more restful, but for the noisy fighter jets in training. Picnic shelters and a dock are also present on the eastern shore.
At one point, Cranberry Lake was a saltwater inlet. The retreating Cordilleran Ice Sheet created a basin about 15,000 years ago, which filled with ocean water. Over time, sand dunes built up a divide between the lake and West Beach. Some saltwater still exists in the depths of the lake.
Cranberry Lake got its name from its history as a cranberry bog used by settlers.