What will I see at Castor Bank?

Divers at Castor Bank in Madagascar commonly report sightings of Humpback whale, Tuna, Green turtle, Spotted eagle ray, and Reef manta ray. Green turtle is recorded as common sightings, while Humpback whale is seasonal, while Tuna, Spotted eagle ray, and Reef manta ray are reported only occasionally. Marine life varies by season and conditions—check the site page for recent diver observations and photos.

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Castor Bank

Nosy Be, MadagascarDirections

Rash guard or 2mm shorty typical

Castor Bank at a glance

Castor Bank is a dive site in Nosy Be, Madagascar. Typically most favorable Feb–Nov · from 3 years of archive data. Divers commonly see Humpback whale, Tuna, and Green turtle. Recent reports put the water around 29°C (85°F). Check the latest conditions and entry details before you go.

No window today· next: tomorrow 6:00–18:00 · favorable

Forecast for this hour · 22:00 · run 14 h ago

0.4 m (1.3 ft)waves — under half a meter expected (waves — about a foot expected)

Tap a factor for its source and model point · Forecast 29°C · seasonal avg 28°C ( · Forecast 85°F · seasonal avg 83°F)

Dive windows this week

Sat

0.4 m waves · 5 kn wind (1.3 ft waves · 5 kn wind)

Sun

0.5 m waves · 6 kn wind (1.5 ft waves · 6 kn wind)

Mon

0.6 m waves · 6 kn wind (2.1 ft waves · 6 kn wind)

Tue

0.6 m waves · 7 kn wind (1.9 ft waves · 7 kn wind)

Wed

0.5 m waves · 5 kn wind (1.6 ft waves · 5 kn wind)

Thu

0.4 m waves · 6 kn wind (1.1 ft waves · 6 kn wind)

Fri

0.4 m waves · 7 kn wind (1.4 ft waves · 7 kn wind)

Favorable windowModerate window— no window

Every forecast dive window each day, site-local time, from wave and wind forecasts. Numbers under each bar are daylight averages.

First light 4:55 · Sunrise 5:16 · Sunset 17:47 · some windows run past sunset

Source: Open-Meteo marine · model point 19 km from site · updated 24 Oct, 08:15 GMT+3

Forecast only — always assess conditions on site.

Compare this weekend’s windows near Castor Bank

Recent diver reports

Dated firsthand observations from divers — not current conditions.

No diver reports for this site yet. — one dated observation helps every diver after you.

Dived here today — did the forecast match?

What Divers Say

Known for: Green turtle, Barracuda, Giant trevally

Based on community reviews and site data. Conditions vary — always verify before diving.

Best months, historically

What conditions have historically been typical at this site, month by month — not a forecast.

January, 78% of days have historically been favorable, water has typically been 30°C (86°F), waves have typically been 1.1 m (3.6 ft), wind has typically been 8 knots
February, 100% of days have historically been favorable, water has typically been 30°C (86°F), waves have typically been 0.7 m (2.2 ft), wind has typically been 7 knots, historically most favorable
March, 100% of days have historically been favorable, water has typically been 31°C (87°F), waves have typically been 0.5 m (1.6 ft), wind has typically been 7 knots, historically most favorable
April, 100% of days have historically been favorable, water has typically been 31°C (87°F), waves have typically been 0.5 m (1.5 ft), wind has typically been 6 knots, historically most favorable
May, 100% of days have historically been favorable, water has typically been 30°C (86°F), waves have typically been 0.5 m (1.8 ft), wind has typically been 6 knots, historically most favorable
June, 100% of days have historically been favorable, water has typically been 28°C (83°F), waves have typically been 0.5 m (1.7 ft), wind has typically been 7 knots, historically most favorable
July, 100% of days have historically been favorable, water has typically been 27°C (81°F), waves have typically been 0.6 m (1.8 ft), wind has typically been 8 knots, historically most favorable
August, 100% of days have historically been favorable, water has typically been 27°C (80°F), waves have typically been 0.5 m (1.8 ft), wind has typically been 8 knots, historically most favorable
September, 100% of days have historically been favorable, water has typically been 27°C (81°F), waves have typically been 0.5 m (1.7 ft), wind has typically been 9 knots, historically most favorable
October, 100% of days have historically been favorable, water has typically been 28°C (83°F), waves have typically been 0.6 m (1.9 ft), wind has typically been 8 knots, historically most favorable
November, 100% of days have historically been favorable, water has typically been 29°C (85°F), waves have typically been 0.5 m (1.6 ft), wind has typically been 8 knots, historically most favorable
December, 98% of days have historically been favorable, water has typically been 30°C (86°F), waves have typically been 0.6 m (2.1 ft), wind has typically been 7 knots

February, March, April, May, June, July, August, September, October, and November have typically had the largest share of favorable days here. Conditions vary year to year — this is historical context, not a forecast.

Based on 3 years of archive data. Bar height shows the share of days each month whose conditions have historically scored favorably.

Marine life seen at this site

Species noted at this site — not a promise of what you’ll encounter.

Species seen here

Rough labels: “Commonly seen” usually means two or more recorded sightings near this site in public dive logs (GBIF), “Occasionally seen” one; “Seasonal” and “Rarely seen” come from dive-guide research. Not a measured rate.