Scuba Diving · San Francisco Peninsula

Scuba Diving 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.

Live conditions, water-clarity forecast, and water temperature for scuba diving in Half Moon Bay, CA. Open the app for a live verdict and a tappable factor breakdown, free, no signup. Pro extends the forecast to 8 days.

Open live conditions →

Conditions snapshot: Oct 5, 2026

Visibility

12 ft

8–20 ft range

Water

59°F

Wind

0 kts

Wave

3.1 ft

Swell

2.1 ft

Period

7.3s

Snapshot from Oct 5, 2026. Live values, factor breakdowns, and 8-day forecast in the app.

Notable species

Half Moon Bay is known for:

LingcodRockfishCabezonHalibutDungeness Crab

Typical water visibility

Summer visibility around Half Moon Bay is commonly reported in the 5–20 ft range, a community-guidance estimate, not a measurement. Rain, river discharge, swell mixing, and seasonality can shift real conditions dramatically day to day.

That's exactly why Submarius exists. The in-app clarity forecast starts from this coast's typical clarity for the time of year, built from in water measurements and satellite ocean color, then subtracts wave stirring, river and runoff plumes, and tide movement to estimate how far you'll actually see, shown as a low to high range, not a seasonal average.

How the clarity forecast 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 5, 2026.

What Submarius shows for Half Moon Bay

Verdict score (0–10). Aggregates wind, swell, tide, moon, and water clarity into one decisive number.
Best window. The 2–3 hour stretch each day when conditions peak.
8-day forecast. Auto-scaled line graph showing which day this week is trending good.
Water clarity forecast. Secchi-depth estimate with uncertainty bounds and the next best vis window.
Free, anonymous. Check conditions with location on, no signup until you want to save spots or post reports.

Safety in the water

Submarius ships OCEARCH tagged-shark alerts, community shark sightings, SOS, and buddy GPS sharing, permanently free, regardless of subscription tier. For Half Moon Bay specifically, the app shows any recent tagged sharks within range and lets you enable push notifications for sightings on your active tiles.