Catalina Island is an hour's ferry ride from Long Beach. San Pedro, Dana Point, and Newport Beach are other departure points for ferries servicing the island.
Avalon, Catalina Island's only city, is very picturesque. It is on a bay surrounded by hills. As your ferry approaches the city, you'll immediately notice the Casino Building (see picture). When you land, you can immediately start exploring the city on foot.
To maximize your time, however, you can take two or more tours of the island. The Avalon Scenic Tour (50 minutes) takes you around the city. The driver/guide will explain to you why there are lots of golf carts on the island. To see the interior of the island, you may take the Skyline Drive (2 hours). You'll see bisons and nice views of the countryside along the way. The Casino Tour (50 minutes) takes you inside the Casino Building. The murals, chandeliers, and other decorations are from a different, more genteel era. There is no gambling in this casino.
There are "sea-based" tours but, being a landlubber, I didn't take any of them. By the way, if you take two or more tours, you'll get a nice discount.
Catalina Island has many fine hotels. There are packages that combine ferries, tours, and hotel accommodations.
Descanso Beach is a short distance from the Casino Building. You may rent a golf cart if you have to travel longer distances.
Catalina Island. Definitely worth a visit. Have a Buffalo Burger (made from real buffalo meat from the buffalo roaming the island, their ancestors were left behind after a movie shoot in the 20's or 30's) at the mile high airport or visit Avalon, the quaint little main town on the Island located some 30 miles south west of L.A.
Catalina Island - I know I have told you to leave LA, but I never told you to leave land to get there, well now I am. Catalina is world famous for its beautiful homes and scenery. You can get to Catalina by fairy or renting a boat at various places throughout the city. When you get there try renting a Golf cart to take you around the island (cars are not allowed on the island), and bring your camera because you WILL need it.
Take a boat trip from Dana Point (situated between LA and San Diego) and visit Catalina Island - superb views from highest point and interesting pub/restaurants. Drive all over this small island in a hired golf cart and soak up the sun. Boat trip takes approx 2 hours from Dana Point, but I believe there are other ports that do the same journey - not sure if they are quicker.