The Foster City Lagoons are hardly an adventure destination, but on a day when there are gale warnings on the bay, they represent a reasonable paddling alternative. There are actually two lagoon systems which are accessed from different launch points.
The principal lagoons in Foster City provide eye-candy for the residents of the dense shore line housing. The public can access them using launch ramps (Boat Park or Ryan Park) or sandy beaches (Gull, Catamaran or Marlin Parks). All sites have free parking and restroom facilities. This is a popular locale for SUPs, novice windsurfers, the occasional outrigger canoe and the ubiquitous electric boats with fringe on top.
Seal Slough which runs through portions of San Mateo and Foster City is accessed from Parkside Aquatic Park in San Mateo. It has beach, ramp and dock launching. This site is also used by a local watersports shop for lessons. Like lagoons in Foster City, the slough is surrounded by dense water front housing, but has more open water.
Free parking, picnic facilities, restrooms and so much more.
Both Foster City lagoons and Seal slough are accessed from Highway 92 which crosses the SF Bay and continues on to Half Moon Bay on the coast. Because I've referenced a number of launch points, I'd advise using your favorite on-line map program to get details.
City of San Mateo - Parkside Aquatic Park website:
Foster City Parks & Recreation website: