Cascade Lake sits in the lower, gentler half of Moran State Park, the 5,000-plus-acre park that covers the middle of Orcas Island and ranks as the largest public recreation area in the San Juan Islands. The swim beach is on the lake's north shore, right where Horseshoe Highway runs past the main day-use area, a few miles north of the hamlet of Olga. Washington's Department of Fish and Wildlife puts the lake at 175.80 acres and 355 feet of elevation, which makes it a small, hill-ringed freshwater basin, nothing like the cold salt water surrounding the island.

Parking takes a Discover Pass. Washington State Parks charges 45 dollars for the annual pass and 10 dollars for a one-day pass, and transaction fees may apply when you buy online or through a dealer. Three paved parking strips run along the road above the beach, all operated by the parks agency and all signed for the pass. If you are trailering a boat, the launch at Midway Campground carries a separate 7 dollar daily fee. Day-use hours are 6:30 a.m. to dusk in summer and 8 a.m. to dusk in winter, and quiet hours run from 10 p.m. to 6:30 a.m.

There is no lifeguard. State park rules put swimming where no lifeguard is present at the swimmer's own risk, and that is the posture here even on the busiest August afternoon. What the beach does have is unusually good support for a small island lake: flush restrooms with wheelchair access about 40 yards off the sand, coin-operated hot showers, drinking water, a playground, and two short piers flanking the swimming water. Fifty-five picnic tables and two kitchen shelters are first come, first served. The log kitchen shelter at the swim area itself can be reserved and comes with a stone fireplace, wood grill, sink and electricity.

The Sugar Shack, the concession stand next to the lake, sells espresso, homemade ice cream sandwiches, swimwear, towels and sunscreen, which covers most of what people forget on the ferry. Orcas Adventures rents stand-up paddleboards, kayaks, canoes, paddle boats and rowboats from the same corner of the day-use area. Both operate weekends from September through May and daily between Memorial Day and Labor Day, so a shoulder-season midweek trip means packing your own everything.

Season here follows the weather more than the calendar. The lake is shallow enough to warm through July and August, and early fall stays pleasant, but it comes up slowly in June and the forested basin keeps it cool. Wind is the local quirk worth knowing. The hills ringing the lake funnel gusts across the surface with little warning, which matters more to paddlers than to swimmers but can turn an easy float back to the beach into work.

Two hazards belong to this water specifically. Cascade Lake is one of only four San Juan County waters carried in Washington's toxic algae sampling database, so a late-summer bloom advisory is a real possibility and worth checking before anyone gets in. And the swim area shares the lake with rental craft, anglers and two docks, so the outer edge of the swimming water is where boat traffic starts. Cascade holds stocked rainbow trout plus cutthroat, kokanee and largemouth bass, and anglers work the shoreline through much of the swim season.

For a longer visit, the Cascade Lake Loop covers 2.7 miles with about 200 feet of gain and crosses a wooden footbridge between the main lake and the lagoon, a quiet arm that people also paddle and swim. The side path around the lagoon runs muddy and overgrown. Four campgrounds hold 124 standard sites and six hiker-biker sites, and North End sits directly behind the swim beach, which is why the parking fills early on July weekends. Dogs are welcome in the park on an eight-foot leash but are barred from designated swim beaches.