Three and One-half Fathom Ledge
Protected Area
Henry Cabot Lodge Bird Sanctuary (Egg Rock)
Why dive here
With 35+ marine species recorded in the area - including nurse sharks - Three and One-half Fathom Ledge offers some of New England's richest reef diving. Water ranges 4-19°C, warmest July, August, September.
Three and One-half Fathom Ledge. Don't let the name fool you, there’s more to this New England spot than a shallow measurement. We love a good rocky reef, and this one delivers with dramatic drop-offs and crevices that shelter some fascinating cold-water characters. Forget the tropical clichés; here, it’s all about the texture of the rock, the way the light filters through kelp, and the surprising resilience of life in a colder ocean. You’ll often find Black Sea Bass lurking in the shadows, and we’ve spotted the occasional Porbeagle shark cruising the deeper edges – a real thrill. Keep an eye out for the Star Ascidian, which adds a splash of unexpected colour against the drab rock. It’s a site that rewards slower diving, letting your eyes adjust to the nuances of the environment. Strong currents can pick up here, so we always plan our dives around slack tide, which generally means better visibility and a more relaxed experience. This isn't a drift dive; it's a place to anchor yourself and explore.
Safety Notes
Cold water this month (avg 15°C). Drysuit or thick wetsuit (7mm+) recommended.
Nearest Dive Centres to Three and One-half Fathom Ledge
Dive shops near Three and One-half Fathom Ledge
Boston Scuba Inc
So. Shore Divers
EC Divers Inc
Undersea Divers
R & R Marine
North Atlantic Scuba
Reviews for Three and One-half Fathom Ledge
Conditions
Ocean conditions, forecast and tides for Three and One-half Fathom Ledge
Three and One-half Fathom Ledge Ocean Conditions
Monthly averages for Three and One-half Fathom Ledge, sourced from Open-Meteo marine data - nearest station: Open-Meteo marine grid (42.6, -70.6) (0km away)
October Averages
Sea Temperature
15°C
59°F · Range: 12.8–18.1°C
Air Temperature
10°C
50°F
Wind Speed
3.78 m/s
7.3 knots
Atmospheric Pressure
1017 hPa
Based on 4 years of monitoring data · Data sources: Open-Meteo marine data
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