Nicobar Islands Dive Conditions: Seasons, Visibility, and Temperature
The Nicobar Islands sit at the convergence of the Bay of Bengal and the Andaman Sea, a position that shapes every aspect of their diving conditions. Unlike the Mediterranean or the Caribbean, where seasonal changes are relatively gentle, the Nicobars are driven by two powerful monsoon systems that fundamentally transform the diving landscape every six months.
Water temperature swings only 3 °C across the year — 27 °C in the coolest months up to 30 °C in the warmest — but visibility ranges from 30 m in peak dry season to 10 m or less during the southwest monsoon. Currents shift from mild and predictable to strong and hazardous. The cyclone window from November to December adds an additional layer of complexity. This guide gives you the month-by-month data so you know exactly when to go and when to stay on the boat.
The Numbers That Matter
| Metric | Range | Best Period |
|---|---|---|
| Water temperature | 27–30 °C (81–86 °F) | April–May (warmest) |
| Visibility | 10–30 m (33–98 ft) | December–April (peak 25–30 m) |
| Current | Mild to very strong | Mild: December–April |
| Air temperature | 22–30 °C (72–86 °F) | December–February (coolest) |
| Rainfall | 3,000–3,800 mm annually | June–September (peak monsoon) |
| Best season | December–April | 5 months of prime conditions |
How the Monsoons Drive Conditions
The Nicobars experience two distinct monsoon seasons — not one — and understanding both is essential for trip planning.
Northeast Monsoon (November – May): This is the diving season. Winds blow from the northeast, across the Andaman Sea, bringing stable weather, calm seas, and reduced cloud cover. Surface conditions are generally flat to slight, visibility is at its annual best, and all dive sites across the archipelago are accessible. This is when the nicobars deliver the conditions that make the transit worthwhile.
Southwest Monsoon (June – September): The wind shifts to the southwest, drawing moisture across the Bay of Bengal. Seas become rough, rainfall intensifies, and surface conditions deteriorate significantly. Visibility drops sharply to 10–18 m. Strong currents from the southwest make exposed sites dangerous. The government ferry from Port Blair is frequently cancelled during these months. Diving becomes limited to protected bays and fringing reefs on the leeward sides of islands.
Transition Months (May and October): These are the shoulder periods when one monsoon is weakening and the other is establishing. Conditions are variable — a week of excellent diving can follow a week of marginal conditions. Planning flexibility is essential.
Month by Month
December – February: Prime Season
Water temperature: 27–28 °C. Visibility: 22–30 m. Current: Mild.
These three months represent the absolute best conditions the Nicobar Islands can deliver. The northeast monsoon is fully established and stable. Seas are calm. Visibility at Campbell Shoal and the Car Nicobar fringing reefs reaches 25–30 m on the best days. The surface chop is minimal — drift conditions are gentle, and shore entries at Galathea Bay and Campbell Bay are straightforward.
December carries the lowest cyclone risk of the early northeast monsoon period. Galathea Bay's leatherback turtle nesting season peaks in January and February — females weighing up to 700 kg come ashore nightly, and the same waters hold post-nesting adults foraging on the reefs. Dugong sightings at Car Nicobar and Katchal are most reliable during this period when the seagrass beds are undisturbed by rough weather.
A 3 mm full wetsuit is comfortable for this temperature range. The water column is well-mixed with no significant thermocline, so you won't hit a sudden cold band at depth.
March – May: Warm Transition
Water temperature: 28–29 °C (April peak 30 °C). Visibility: 18–25 m. Current: Mild to moderate.
March is still excellent — visibility holds at 22–25 m, and water temperature climbs to a comfortable 28 °C. April sees the warmest surface temperatures of the year at 29–30 °C, but visibility begins to drop as plankton production ramps up. A 3 mm shorty is sufficient by late April.
May is the transition month. The northeast monsoon weakens, and the southwest monsoon's first signs appear toward the end of the month. Winds pick up, particularly in the afternoons. Visibility drops to 18–20 m. Access to exposed sites — Indira Point and Nancowry-Kamorta Channel — becomes weather-dependent. This is still a diving month, but planning needs to account for the advancing monsoon. Any expedition in May should schedule the most exposed sites early in the trip.
June – September: Southwest Monsoon
Water temperature: 28 °C. Visibility: 10–18 m. Current: Strong to very strong.
Diving is not recommended during these four months for any non-essential expedition. The southwest monsoon brings sustained high winds, heavy rainfall (300+ mm per month), and rough seas. The government ferry from Port Blair is frequently delayed or cancelled. Most dive sites are inaccessible.
Visibility drops to 10–15 m on the exposed west-facing reefs, with particulate matter from runoff and wave action reducing clarity significantly. The strong southwest currents create hazardous conditions, especially at channel sites like Indira Point and Nancowry-Kamorta. Only the most sheltered fringing reefs — Campbell Bay's north-facing patches and some Car Nicobar bays — offer any realistic diving, and even those come with reduced visibility and challenging surface conditions.
If your expedition schedule is flexible, the very end of September can offer a brief window as the monsoon begins to weaken, but this is unpredictable. Plan for June–September as a no-go window and build your schedule around the November–May season.
October – November: Recovery and Cyclone Risk
Water temperature: 28 °C. Visibility: 18–25 m (improving). Current: Moderate.
October is the transition back to favorable conditions. The southwest monsoon tapers off, winds ease, and visibility climbs back toward 20–25 m. The northern sites around Car Nicobar and Tillangchong become accessible again by mid-October. Water temperature remains at 28 °C — comfortable in a 3 mm suit.
November is when the northeast monsoon begins to establish itself, and conditions improve rapidly. Visibility reaches 20–25 m, seas calm, and the full archipelago opens up. However, November also falls within the Bay of Bengal cyclone season (peaking October–December). The Nicobars are less cyclone-prone than the northern Bay of Bengal, but sea states can be affected by distant systems. Monitor the India Meteorological Department for cyclone warnings in the weeks before and during any November expedition.
December arrives with excellent conditions that carry through until the following May.
Site-Specific Conditions
Not all sites respond to the seasons the same way. Here is how the four main diving areas behave across the year:
Campbell Shoal (seamount, 5–40 m): This is the standout site in the archipelago and the most consistent across the season. The seamount's upwelling effect creates its own microclimate — visibility can remain above 20 m even during the monsoon, and current is driven more by tidal flow than monsoon wind. Best conditions: January–April. Seasonally accessible: November–May.
Galathea Bay Coral Reefs (fringing reef, 2–25 m): Protected by its bay geography, Galathea is one of the most reliable sites during marginal conditions. The shallow seagrass beds and mangrove channels are sheltered from the worst of the southwest monsoon. Turtle nesting determines the human presence (December–April), but the reef is diveable year-round for permitted expeditions. Best conditions: December–April.
Indira Point Reefs (drop-off, 3–30 m): The most current-sensitive site in the archipelago. Exposed to the full fetch of the Six Degree Channel, this site demands calm conditions. Diveable December–April. Inaccessible June–September. During May and October–November, check the forecast carefully — strong channel currents can make this site dangerous even when other sites are fine.
Car Nicobar Fringing Reefs (fringing reef, 2–20 m): The protected bays of Car Nicobar offer the calmest diving in the archipelago. The northern location means Car Nicobar sees slightly better conditions earlier in the northeast monsoon season (starting November) and slightly better conditions later in the southwest monsoon (through October). Dugong sightings are most reliable here, and the calm, shallow waters make this the most beginner-friendly zone in the Nicobars.
Gear Notes
Wetsuit: A 3 mm full wetsuit covers December through May comfortably. The water temperature range is narrow (27–30 °C), so a 5 mm suit is not needed. For monsoon season expeditions (June–September), a hooded 5 mm may be preferred as wind chill and surface exposure become factors.
Exposure for deep dives: Campbell Shoal and Indira Point both reach 30–40 m. The thermocline is mild during the northeast monsoon (1–2 °C drop) and more pronounced during the transition months. A hood is not essential but is nice to have for the deeper dives.
Current gear: Seamount and channel dives at Campbell Shoal and Indira Point require comfortable use of a surface marker buoy (SMB). Bring your own — none available on the islands. A reef hook is recommended for Campbell Shoal during high-current days.
Equipment self-sufficiency: Every piece of gear you need must arrive with you. There are no dive shops, no fill stations, no rental equipment, and no repair services in the Nicobar Islands. Bring backup regulators, spare O-rings, a full tool kit, and a portable compressor if your expedition involves more than a few days of diving. This is not optional — it is the defining logistical reality of diving this destination.
Putting It Together
The Nicobar Islands offer a 5-month window of excellent diving (December–April), a 2-month shoulder window (May and November) with variable but manageable conditions, and a 4-month period when diving is effectively off the table (June–September). The cyclone risk in November–December adds an element of uncertainty that expedition planners need to budget for.
Plan your expedition for January or February for the safest bet. March offers identical conditions with slightly warmer water. November expeditions should carry contingency plans for cyclone-related weather delays. Avoid June–September entirely unless your purpose is scientific and you have a flexible window measured in weeks, not days.