SCUBA diving in Izu Oshima is somewhat unique from other dive sites at similar range of latitude world wide. Since the island is about 40km remote from mainland, and partially affected by warm Black Current from Philippine Sea, water is clear and extremely wide variety of marine lives are seen. Different creatures and different habits are observed at every time of dive even though you dive the same point repetitively.
Guided dives by extremely knowledgeable staffs are another great advantage in this island. Since those staffs dive the same place almost everyday, sometimes more than once a day, they know almost every pieces of creatures living in every holes and cracks of rocks. They not only just give you names of those creatures but also brief you how they lives, such as holding and protecting eggs, and how they grows.
The island is surrounded mostly by rocky coast, but sandy beaches are limited. There are no coral reefs along the coast, but some hard corals can be seen in limited places. Warm water current, so called Black Current, from Philippine Sea is flowing off southern end of the island, and partially reaches west coast of the island. This current brings many kinds of sea lives from tropic ocean, and those are often seen during September to December. However, as water is cooled down by strong cold wind from North in winter season, those tropical creatures die and disappears.
Another current with cold and nutrition rich water is flowing from deep see floor to east coast surface of the island. Therefore many fishes from small to big are gathering to these area. Huge school of sardines, snappers are often seen, especially during the autumn season. Jack fishes, tunas, sharks and even whales are also found chasing those schools quite often.
Water temperature rises to 24C at highest during September-October, but drops down to 14C at lowest during March-April.
I have prepared a detailed guide to Izu Oshima for foreign divers convenience at the following URL.
Facts about Izu Oshima
It is in Japan- Izu Oshima is in the Pacific.
- The typical depth is 0-50 Metres 0-160 Feet.
- The typical visibility is 10-30 Metres 30-100 Feet.