Diving seasons: where the water is good each month

Somewhere in the world there is good diving every month. What changes is where. In the tropics, the monsoon decides the season: it brings wind, swell and rain to one coast while the other side of the same country stays calm. Many big animals also keep to a calendar of their own, so a trip to see mantas, whale sharks or humpbacks has to be timed more closely than a trip for reefs.

Month by month

• December to April: the Andaman Sea, the Maldives, Raja Ampat, Palau and Chuuk are all at their best. Most of the Caribbean is dry.
• May: a changeover month. The Red Sea is warming up, Borneo's Sipadan area is in season, and the Andaman side of Thailand is starting to get rough.
• June to October: the Great Barrier Reef has its clearest water, the Galápagos is cold and full of life, and the Gulf of Thailand is calmer than the Andaman coast.
• September to November: the Red Sea is warm and settled again before winter, and Raja Ampat comes back into season.

Indian Ocean and Thailand

In the Maldives, the dry north-east monsoon from December to April brings the calmest seas and the best visibility. The wet season from May to November is not a write-off: plankton blooms then bring mantas and whale sharks to the western atolls, and Hanifaru Bay in Baa Atoll is famous for manta feeding from about June to October.

Thailand has two coasts with opposite seasons. On the Andaman side, around Phuket and Krabi, the season runs from November to April, and the Similan Islands National Park is only open from mid October to mid May. On the Gulf side, around Koh Samui and the dive island of Koh Tao, the rain comes later, from October to December, so the Gulf is the place to go in the middle of the year.

The Seychelles are best in April and May and again in October and November, the calm weeks between the two trade winds.

Indonesia, Malaysia and the Western Pacific

Raja Ampat has more coral and fish species than almost anywhere on Earth. Liveaboards run from October to April, when the sea is calmest; from June to September the south-east wind makes crossings rough. Around Labuan Bajo and Komodo National Park you can dive most of the year, but the currents are strong, and the dry months from April to November are the most comfortable.

Semporna is the base for Sipadan, off the east coast of Sabah, known for turtles and huge schools of barracuda. The best months are March to October, and only a limited number of permits are issued each day, so book ahead.

In Bali, July to October is the season for the oceanic sunfish (mola mola) at Nusa Penida, where cold water rises from the deep.

Palau is at its best from November to April, with steep walls, strong channels and grey reef sharks at Blue Corner. In Chuuk, dozens of Japanese ships sunk in 1944 lie in the lagoon; the dry season from December to April is the time to go.

Australia

The Great Barrier Reef and the Whitsundays are best from June to October: drier, clearer and outside the box jellyfish season, which runs roughly from November to May. Dwarf minke whales visit the northern reef in June and July, and humpbacks pass through from July to September.

Red Sea

The Red Sea off Egypt can be dived all year, and the water rarely drops below about 21°C. Spring and autumn are the most pleasant: in summer it is very hot on land, and in winter the wind picks up. Eilat, at the northern tip of the Gulf of Aqaba, has calm, sheltered reefs and is good from autumn to spring.

Americas and Okinawa

The Galápagos has two seasons. From June to November the cold Humboldt Current brings plankton and whale sharks to the far northern islands of Darwin and Wolf, though the water is cold and the sky often grey. From December to May the water is warmer and calmer, with better visibility. Hammerheads school around Darwin and Wolf all year.

Near Cancún, whale sharks gather off Isla Mujeres and Holbox from about June to September, most reliably in July and August. September is also the height of the hurricane season, so leave room in your plans. Inland, the cenotes of the Yucatán can be dived all year.

In Okinawa, humpback whales come to the Kerama Islands from January to March, and the summer is good for diving except when a typhoon passes.

Tips

• Always check which coast or atoll you are going to. "Thailand" or "the Maldives" in the wrong month can mean a very different sea.
• Liveaboards to remote areas often only run in the best months, so their schedules are a good guide to the season.
• If you want a particular animal, plan around its season first and the weather second.