What the diving is like
Ambon Bay cuts deep into the island of Ambon from the southwest, almost dividing it into two peninsulas, with steep hills of 300 m to 700 m rising behind both shores. Near Poka and Galala the bay narrows to a few hundred metres over a sill only about 12 m deep. Beyond the sill the inner bay is a shallow basin of about 40 m, while the outer bay deepens quickly towards the Banda Sea. The sill limits the exchange of water with the open sea, so silt from the surrounding hills settles in the inner bay and visibility there is seldom more than moderate.
The muck sites lie mainly along the northern shore of the outer bay around Laha, near the airport, and along the opposite shore at Amahusa. Typical bottoms are slopes of fine grey or black sand, rubble and stones, with patches of algae, sponges and the occasional coral block. The silt is very fine and lifts at the slightest fin movement, so good buoyancy control is more important here than at destinations with heavier sand.
The bay is also a working harbour. Jetties, fishing boats and the villages along the shore have left tyres, nets, bottles and wood on the bottom, and the animals use this debris as shelter in the same way as the natural rock and rubble. Jetty dives under sponge-covered pilings are a regular part of the diving, by day and at night. In the north of the bay the cargo ship Aquila, 137 m long, has lain at 15 m to 35 m since it sank in 1958.
Outside the bay the south coast of the island is a different kind of diving, with walls, caves, swim-throughs and a rock arch in clearer and deeper water.
Critters
Ambon is best known for frogfish, and above all for the psychedelic frogfish, which was first photographed in the bay in 2008 and described as a new species the following year. The hairy frogfish and several smaller frogfish are recorded as well. The scorpionfish group is also well represented, with the Ambon scorpionfish, named after the island, and rhinopias among the records.
The cephalopods include several octopus species and the flamboyant cuttlefish, and the seahorses and pipefish include ghost pipefishes. Nudibranchs and sea slugs, crustaceans and mandarinfish among the muck fish complete a fauna that has been studied for a long time: a survey published in 1863 already recorded 783 fish species from the bay.
Conditions through the year
Water temperature in the bay ranges from about 26 °C to 30 °C. It is warmest, at about 29 °C to 30 °C, from November to April, and coolest at about 27 °C in July and August.
Visibility inside the bay is usually 5 m to 15 m and depends heavily on rainfall, because run-off from the hills carries silt into the water. It tends to be best in the drier months from about October to April and lowest in the wet months of the southeast monsoon. The sites on the outer coast often have clearer water than those inside the bay.
The shape of a day
Most dive operators are on the northern shore of the bay, close to the muck sites, and many sites are reached by a short boat ride or directly from a jetty. Operators state between two and four dives a day, often with a night dive, and some also offer blackwater dives. Fewer divers visit Ambon than the busier muck destinations, and a group is often the only one on a site.
Trips to the walls and caves of the outer coast depend on the sea state outside the bay and are most practical during the drier months.
Getting there
Pattimura airport (AMQ) is on the northern shore of Ambon Bay, a short drive from the muck sites, and some dive resorts are about ten minutes from the terminal. There are no international flights. Direct domestic flights arrive from Jakarta, taking about three and a half hours, and from Makassar, the busiest route, as well as from Surabaya, Denpasar, Manado, Sorong and Ternate.
Because every route involves at least one domestic flight, connecting times and baggage allowances need planning, especially for anyone travelling with camera equipment.
Combining it with other trips
The Banda islands, southeast of Ambon in the Banda Sea, are the most common combination. They are reached by fast boat from Tulehu on the east coast of Ambon, a crossing of about five hours, or by slower passenger ships; schedules change often and should be checked close to the date of travel. Banda offers clear-water reef and wall diving, a contrast to the silt of the bay.
Ambon's direct flights to Manado and Sorong make it a natural stop on a longer trip, either combined with the black sand of the Lembeh Strait or with the reefs of Raja Ampat. Liveaboards in the Banda Sea and the Maluku islands also begin or end in Ambon.
When to come
The usual diving season is October to April. Ambon's seasons are the reverse of much of western Indonesia: the southeast monsoon from about June to August is the wettest period, with June and July the wettest months, while the northwest monsoon from about December to February is relatively dry and November is usually the driest month.
During the southeast monsoon, strong winds and heavy rain make the bay rougher and reduce visibility, and some operators reduce or suspend diving between about July and September. The inner sites remain more sheltered than the outer coast, which takes the full force of the southeast wind.