Submarius
Dive conditions in Half Moon Bay
The coast just south of San Francisco: Pillar Point harbor, the big wave reef at Mavericks, and productive rockfish and lingcod grounds. Cold, often green, big swell water. A fishing and spearfishing coast where timing the swell window is everything.
Before you dive, open the app for the swell, wind, tide, water temperature, current and a visibility estimate for Half Moon Bay, CA.
Notable species
Half Moon Bay is known for:
Typical water visibility
Summer visibility around Half Moon Bay is commonly reported in the 5 to 20 ft range, a community guidance estimate, not a measurement. Rain, river discharge, swell mixing, and seasonality can shift real conditions dramatically day to day.
The app shows a model estimate of today's visibility here, with a confidence figure.
How the visibility estimate works →Clearest months at Half Moon Bay
Model climatology from the baked clarity ceiling: the typical day and the best case (90th percentile) visibility for each month, with a seasonal algae bloom proneness flag. These are labelled model estimates, not measurements.
| Month | Typical ft | Best case ft | Bloom risk |
|---|---|---|---|
| Jan | 20 | 20 | low |
| Feb | 20 | 20 | low |
| Mar | 20 | 20 | low |
| Apr | 16 | 20 | low |
| May | 16 | 20 | low |
| Jun | 10 | 20 | low |
| Jul | 11 | 20 | low |
| Aug | 10 | 13 | low |
| Sep | 11 | 21 | low |
| Oct | 12 | 20 | low |
| Nov | 16 | 24 | low |
| Dec | 17 | 20 | low |
Ceiling artifact global-reef-v10-obis-world; table baked Oct 15, 2026.
What Submarius shows for Half Moon Bay
This page reads Half Moon Bay at 37.46°N, 122.43°W, in San Francisco Peninsula. Open the same point in the app for:
- A 0 to 10 rating. For diving at Half Moon Bay today, from Rough to Prime, and you can tap any factor to see why.
- Best 3 hour window. The three hours in the next 24 that score best.
- Tide. Rising, falling or slack, the next high or low, and a 24 hour curve.
- Wind. Speed and direction, with gusts.
- Waves and swell. Wave height and swell, with the second and third swell by the hour.
- Water temperature. With the air temperature underneath.
- Current. Drift in knots and the next slack, from a regional model, so it's offshore drift, not your entry.
- Visibility estimate. A model estimate with a confidence figure, not a measurement.
- Weather warnings. National Weather Service warnings for this spot and its marine zone.
- 8 day forecast (Pro). Days 2 to 8, hour by hour.
Reefs and wrecks near Half Moon Bay
The reefs and wrecks layer in the app marks charted wrecks, reefs and obstructions around Half Moon Bay, where sources have them. Tap one for the seabed depth beside it (an estimate where no chart reports one), the least depth over the structure where a chart sounding exists, and today's conditions at that spot. The structures are merged from NOAA nautical charts and other public sources, so coverage is densest in US waters. It's a Pro map layer.
See the spearfishing map →Safety in the water
Every safety tool in Submarius is free. With Safety Watch you set a "back by" time and pick who watches. If you don't check in by then, the server alerts them by push or email, even if your phone is dead. It needs a free account and never contacts the coast guard.
When Spearfishing is your mode, a shark awareness card also lists the shark species recorded in the area and any community sightings from the last 48 hours.
Also at Half Moon Bay
More diving locations
See all →Check Half Moon Bay before you head out
Today's conditions, safety tools and trip recording are free. Pro adds the 8 day forecast, the Pro map layers, cam playback and offline areas for $12.99 a month or $99 a year, or $149 once (US prices).