San Mateo Marina Lagoon: toxic algae advisories
San Mateo Marina Lagoon, San Mateo County. See all San Mateo County waters.
What the state's records say
Caution advisory, last posted Jun 26, 2026. No all-clear recorded.
2 reported spots here have an advisory with no all-clear recorded.
Reporting is voluntary, so the state may not have recorded an end even if conditions changed. Check posted signs and the official map.
What this level asks: Algae that can make toxins may be present. Keep people, children and pets away from algae and scum, and do not let pets drink the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at San Mateo Marina Lagoon
The state has an advisory on file for San Mateo Marina Lagoon (Caution advisory), last posted Jun 26, 2026, and no all-clear recorded. Keep your dog out of the water and away from scum on the shore until the state records an end.
Reported spots
The state records each report at a spot, such as a beach or a boat ramp. Each spot's latest deciding record:
| Spot | Status |
|---|---|
| Parkside Aquatic Park 1 | Caution advisory, last posted Jun 26, 2026. No all-clear recorded. |
| Lakeshore Park | Caution advisory, last posted Aug 28, 2025. No all-clear recorded. |
Advisory history
Every advisory record the state has published for San Mateo Marina Lagoon, newest first. "None" is the state's record that no advisory was recommended on that date. "NA" records do not change a status.
| Date | Spot | State's level | Notes |
|---|---|---|---|
| Jun 26, 2026 | Parkside Aquatic Park 1 | Caution | Bottom/benthic bloom observed |
| May 21, 2026 | Parkside Aquatic Park 1 | Caution | Bottom/benthic bloom observed |
| Aug 28, 2025 | Lakeshore Park | Caution | Bottom/benthic bloom observed |
| Aug 28, 2025 | Parkside Aquatic Park 1 | Caution | Bottom/benthic bloom observed |
| Jun 19, 2025 | Lakeshore Park | Caution | Bottom/benthic bloom observed |
| Jun 19, 2025 | Parkside Aquatic Park 1 | Caution | Bottom/benthic bloom observed |
Source
Advisory data: California State Water Resources Control Board, Freshwater Harmful Algal Bloom Program, via data.ca.gov (public domain). Advisories are recommendations; reporting is voluntary and incomplete. The state's data. An advisory ends only when the state records a later "None" (no advisory recommended) at the same spot, or an end date. A blank end date is unknown.