Marina Lagoon

There are three larger public parks off of Marina Lagoon, Lakeshore Park, Parkside Aquatic Park, Joinville Park and at the outlet Seal Point. The lagoon, or Seal Slough is a remnant of a tidal slough that was diked and dredged. It is managed to serve as the City’s flood control basin, recreation area, aesthetic amenity, and ecological resource. The lagoon winds north from its inlet at the Belmont city limits to its outlet at Seal Slough, a distance of about 4 miles. The lagoon ranges from 300 to 400 feet wide, with side slopes of 5:1 for stability and is 6 feet deep in the center during the summer. Details on swimming and boating are below. The lagoon is drawn down between January 15 and February 15 each year for pier and other repairs and maintenance to houses and docks.

Marina Lagoon Harbor Patrol

1500 Marina Ct, San Mateo, CA 94403

On duty (650) 740-3340

(650) 522-7467 Station at Parkside Aquatic Park

Memorial Weekend through September: Weekends and Holidays: 9am to 9 pm

Mid June through Labor Day: hours vary with weather & activity

Lakeshore park is offers three areas with a few picnic tables that can be reserved for $60 and one free drop in picnic table. Alcohol may be served in Lakeshore Park only with a $50 alcohol permit. Inflatable jumpers are permitted with some limitations and a $25 jumper permit.

  • Baseball Diamond
  • Basketball Court
  • Picnic Areas
  • Playground
  • Restrooms

The lagoon’s primary water source is tidal flow from San Francisco Bay through O’Neill Slough. Bay water is augmented by a low volume of fresh water inflow from Laurel Creek in the 10.3 square mile watershed and stormwater runoff.

The Harbor Patrol provides enforcement of regulations and boat inspection assistance and first aid, from Memorial Weekend through Labor Day.

Water samples are sampled each week at Lakeshore and Parkside Aquatic Park beaches for concentrations of indicator bacteria.

Boating Zones

ZONE A From the dam near 3rd Avenue south to the posted point opposite
the prolongation of Harrison Avenue. Power boating and water skiing. 35 mph limit.

ZONE B From the end of Zone A to a point 500 ft south of the exisitng
Highway 92/19th Avenue overpass. All boats. No wake -5 mph.

ZONE C From the end of Zone B to a posted point approximately 400
feet north of Lakeshore Park and Beach. All boats, No skiing. 35 mph.

ZONE D From the end of Zone C to a point approx. 200 feet south of
Hillsdale Blvd. bridge. Sailing area. No skiing, power boats traverse
only. No wake -5 mph

ZONE E From the end of Zone D to a posted point oblique to the prolongation
of 40th Avenue. Power boating and water skiing. Other craftn traverse only. 35 mph.

ZONE F From a posted point at the end of Zone E to the end of the
lagoon. Hand and sail powered vessels only. Fishing permitted, no
swimming. No wake – 3 mph.

ZONE G Northern-most cove. Open to all craft. No swimming. No
wake- 3 mph.

ZONE H South cove at northern end of Marina Lagoon. Open to all craft.
Fishing permitted, no swimming. No wake – 3 mph.