Colman Park has no lifeguard. Seattle Parks and Recreation does not include it on the city's list of guarded swimming beaches, so anyone swimming here is on their own, with no staff on the shore and no rescue equipment kept on site. The nearest guarded water is Mount Baker Beach at 2521 Lake Park Drive South, about a quarter mile south along the same shoreline and an easy walk. Mount Baker is guarded from late June through the first week of September, weekdays noon to 7 p.m. and weekends 11 a.m. to 7 p.m. Outside those dates and hours the whole shoreline, Colman and Mount Baker alike, is unsupervised.

Swimming here is permitted and the access is genuinely public. The park drops 24 acres of wooded hillside from 31st Avenue South down to Lake Washington, and its lower edge is continuous city-owned lake frontage. A paved path runs down to the water at the north end and finishes in a concrete apron with a short flight of cement steps going straight into the lake. Those steps are what survives of the park's old swimming area. The beach next to them is a thin strip of gravel rather than a broad sand strand, and the bottom drops away quickly off the apron. Four benches face the water. There are no restrooms in Colman Park; the closest are over in Mount Baker Park.

This shoreline was Seattle's first municipal waterworks. A steam pumphouse built here in 1884 pulled drinking water out of Lake Washington and pushed it up to a Beacon Hill reservoir, and James M. Colman, whose name the park carries, worked 36 hours straight to restart the pump when eastern engineers had given up on it. The station ran flat out during the Great Seattle Fire of 1889. Once the Cedar River pipeline took over in 1901 the site went to the Park Board, the state granted the shorelands for park purposes in 1909, and the Olmsted Brothers worked the ground into their boulevard plan. By 1915 a building beside the pumphouse was serving as a bathhouse and roughly 40,000 swimmers a year were using the beach, with a concession stand, changing rooms and a long dock out into the lake. A campaign to save the pumphouse failed and it came down in 1965, which ended the official beach. Colman Park and the Dose Terrace Stairs were listed on the National Register of Historic Places on February 10, 2020.

Public Health Seattle and King County samples around thirty lake swimming beaches every week, testing for bacteria from mid-May to mid-September and for toxic algae from early June into late October. Beaches are ordered closed when either reading runs high, and that happens often enough on Lake Washington in a warm summer to be worth checking before driving over. Routine sampling is concentrated at the guarded beaches, so Mount Baker Beach has a published record and the Colman Park shore a few hundred yards north does not, though the two sit in the same water.

There is no fee. Seattle Parks and Recreation charges nothing to enter the park, nothing to park and nothing to swim. Gates are open 6 a.m. to 10 p.m. The address is 1740 Lake Washington Boulevard South. A lot at the bottom of the hill holds about 22 cars and fills on hot afternoons; Metro route 27 comes down into the lower park. A pedestrian tunnel under Lakeside Avenue links the waterfront to the hillside trails and the P-Patch above, and the paved lakeside path here runs uninterrupted south to Seward Park. On scheduled summer weekends Lake Washington Boulevard closes to through traffic for Bicycle Weekends, which makes the approach from Leschi or Seward Park considerably quieter.