We've made a couple of trips to Ita Beach south of Cape Ose on the west coast of the Izu pennisula. From Yokosuka we spent around 1600 yen on tolls. 700 yen for parking. In the summer they charge 300 yen per diver. In the winter it's only parking. Only other costs will be gas which will vary depending on what you're driving. The drive (if you don't get lost) is between 3-4 hours from Yokosuka (south of Yokohama) We went right off the beach. There is a fairly substantial pier there and a local dive shop that runs dives and classes from there. We head down to the south end and enter the water there. We try to avoid getting in anyones way.
The entry is over rocks, but we only have to make our way about 20-30 feet before we're in the water. It drops off fairly quickly. Pretty nice fish life, lots of morays. I've even seen dragon morays both time I've been there. It drops down to over a 100 feet. Rocks, corals... vis has been good both times that I've been there, 50ft+. Water temp the end of September was mid 70's. Water temp first weekend in February was mid 50's. I wore a 3mm in September, a drysuit in February.
It makes for a nice day. If you get up early enough (and don't get lost ;) ) you can drive down in the morning, get in 2 or 3 dives and be back by evening. It's a very scenic drive. You have good views of Mount Fuji usually from the west coast of Izu.
If you stay overnight, Izu is known for the many onsen (natural hot springs) which often have hotels associated with them..
