Deep Lake

Deep Lake is the 63-acre lake inside Millersylvania State Park, south of Olympia in Thurston County. The park holds about 3,300 feet of its shoreline, with two swimming beaches, a fishing dock and a hand-carry boat launch. Boats are limited to 5 mph with no wake, which keeps the water calm for swimmers, kayaks and paddleboards.

Which Deep Lake?

Washington has several lakes called Deep Lake. This one is in Thurston County, inside Millersylvania State Park at 12245 Tilley Road S, Olympia. The Deep Lakes near Colville, in King County and in Grant County are different lakes.

The Lake in Numbers

• Surface area: 62.9 acres, according to the Washington Department of Fish and Wildlife.
• Depth: Washington State Parks' history page calls it "17-foot-deep Deep Lake."
• Elevation: 198 feet.
• Park shoreline: about 3,300 feet of freshwater shore, per the park brochure.
• Speed limit: 5 mph, no wake.

Swimming

The park has two swimming beaches on the lake, close to the day-use parking and the kitchen shelters. Dogs are not allowed on designated swim beaches, and glass bottles and metal cans aren't allowed there either. See swimming.

Paddling and Boating

The launch is hand-carry only, with a 100-foot dock, so trailered boats can't launch here. That suits kayaks, canoes, paddleboards and small car-top boats. Washington State Parks recommends Deep Lake for learning to paddleboard because the water is calm and the parking lot is near the lake. From Memorial Day to Labor Day you can rent kayaks, paddleboards, canoes, pedal boats and tubes at the beach by the launch. See boating and rentals.

Fishing

Deep Lake is open to fishing all year. WDFW stocks it with rainbow trout, and the lake also holds naturally reproducing largemouth bass, bluegill, yellow perch and pumpkinseed sunfish. Fish from the dock, the bank or a car-top boat. Two-pole fishing is allowed. You need a WDFW fishing license as well as a Discover Pass to park. See fishing.

When to Go

• Summer is busiest: the beaches, rentals and the taphouse all run Memorial Day to Labor Day.
• Spring and fall are quieter for paddling and fishing.
• Winter: the lake and the launch stay open. Day use runs 8 a.m. to dusk.

Water Quality

Washington State Parks warns that toxic blue-green algae can bloom in lakes, usually in mid to late summer, and may look like spilled blue-green paint on the water. If the park posts a warning, or the water looks wrong, keep people and dogs out.