Catalina Island is the most obvious major day trip from Long Beach because the journey begins right on the waterfront. After travelling across the channel, you arrive in an island environment that feels far removed from the urban coast you left behind.
Avalon is the main destination for most first-time visitors. The compact town is easy to explore on foot and sits around a picturesque harbour backed by steep hills.
Can you do Catalina in one day?
Yes. A day trip gives you enough time to walk around Avalon, have lunch and choose one or two activities. But ferry schedules define your day, so avoid trying to fit in everything the island offers.
Hiking, water activities and tours can take you beyond the immediate town if you have enough time.
Consider staying overnight
An overnight visit changes the pace considerably. Once many day visitors depart, Avalon becomes quieter and you have more flexibility to explore.
Ferry schedules, fares and reservation requirements change, particularly by season, so check current information and book ahead when demand is high.
I would choose Catalina when you want one excursion that feels genuinely different from Long Beach. The ferry ride itself is part of the experience, and arriving on an island by sea gives the day a sense of travel that a freeway trip rarely manages.