The swimming beach at Seward Park sits on Andrews Bay, the sheltered water along the west side of the Bailey Peninsula, roughly five miles southeast of downtown Seattle. Seattle Parks and Recreation runs it and charges nothing for any of it. No entry fee, no parking fee, no charge for the lifeguards, and no charge for the beach swim lessons the department offers to kids aged 6 to 16. The address is 5900 Lake Washington Blvd S and the park is open 6 a.m. to 10 p.m. This one stretch of sand is the designated swimming area. The rest of the peninsula's shoreline is riprap and steep bank, so the beach is where you get in.

The guarded season is short. In 2026 it ran June 27 through September 7, with lifeguards weekdays from noon to 7 p.m. and weekends from 11 a.m. to 7 p.m. Seward Park is one of the few Seattle beaches kept staffed through the late-season window after most others close in late August. A floating platform is anchored offshore and there is no diving board, which fits the gradual sand entry. Outside those dates the beach stays open and unguarded.

Water quality is the thing to know here. Andrews Bay is one of only two parts of Lake Washington, along with Union Bay, that lacks the steep sides and roughly 200-foot floor found across the rest of the lake. It is shallow and it flushes slowly, which is the condition that concentrates whatever washes in. Public Health Seattle and King County has closed this beach more than once. Samples pulled June 17, 2024 put Andrews Bay Beach under a stay-out-of-the-water advisory alongside Enatai and Houghton. Samples taken in May 2026 came back at 1,200, 690 and 680 colony-forming units per 100 mL, far above the 320 threshold that triggers a closure when two or three samples exceed it, and the advisory held until later that month. In August 2015 a sewage spill into Lake Washington shut the beach for days.

Checking before you go takes a minute. King County samples the beach weekly, usually Monday or Tuesday afternoon, from mid-May to mid-September, and posts all three results in a table and map at kingcounty.gov/swimbeach. You can sign up on that page for an email or text every time Public Health closes or reopens a beach, plus a Friday status summary. Toxic algae is a separate program. The county collects cyanobacteria samples from early June into late October whenever a bloom is visible, and toxin results are published at nwtoxicalgae.org. When a beach is closed, Seattle Parks puts a banner on the park page and signs at the water. Routine testing stops for the winter, so from late September until mid-May there is no fresh number and the posted signs are all you have.

The forest above the beach is worth the walk. About 120 acres of the park's 300 hold the largest stand of old trees left inside Seattle, the ground the Olmsted Brothers named the Magnificent Forest when they wrote the peninsula into the city's 1903 parks plan. Douglas fir dominates, with western red cedar, bigleaf maple and madrona mixed through it. Bald eagles nest there. Dirt trails climb off the paved 2.4-mile shoreline loop into the interior, and the drop in noise is sharp enough that Seward Park carries an Urban Quiet Park designation.

A few practical things. Seattle bought Bailey Peninsula in 1911 for $322,000, and the wide grassy meadow you cross to reach the sand exists only because the Ship Canal lowered Lake Washington in 1917. The bathhouse went up in 1927. Andrews Bay has a 3-knot vessel speed limit and is a well-used anchorage, so there will usually be boats offshore. Hand-carry launches sit at Andrews Cove north of the clay studio and on the south shore. Restrooms, drinking fountains, picnic sites and grills are on site, and the Audubon Center and clay studio are a short walk from the beach.