There are two recommendable dive shops in the Los Angeles area that I have dived with. Aloha Dive (Chris Russello, the owner) and Ventura Dive and Sport (Jim).

They both have their own boats. Breakfast and/or lunch is included, depending on the boat.

Aloha Dive’s boat, the Great White, uses an air compressor, so you only need one tank to make 2 or 3 dives. Ventura Dive and Sport’s boat, the Raptor, will already have tanks on the boat, but no compressor. So each person uses three separate tanks, which means you’ll have to replace your gear.

The Raptor is also a very fast boat, so you’ll get there sooner and come back sooner. If you do use them, I recommend getting lunch at the restaurant across the parking lot from them. Their clam chowder is very popular.

You may also want to check out Catalina Island. You can take a ferry out there and rent gear on the island. Aloha Dive may dive out there as well.

Compared to tropical waters, it is colder out here. You will need a hood, a thicker wet suit and gloves in addition to your booties.

If the shops only sell the hoods/gloves, you can rent at sport chalet. However, I don’t recommend diving with Sport Chalet because you won’t get your money’s worth.

You may also want to read up on marine life as well as what you can find above the surface (last two links).

Good luck!