Riverside is quite a ways from any beach... the closest is 60 miles or so. Laguna Beach has some tide pools. The others are quite a ways, such as Cabrillo Beach, or way down south in La Jolla (or up north in Carpinteria).
There are no beaches near Riverside as Riverside is quite a ways inland. But it s worth the drive to spend a day at Abalone Cove Shoreline Park in Palos Verdes. Bring a picnic lunch, pack some towels in a backpack and hike down to Abalone Cove where there are tons of tide pools with crabs, fish, starfish, sea anenomes, shells, etc.It s a very affordable but great outing for kids and the hike is very easy so you can get some exercise and then enjoy the beach and tidepools once you get to the bottom.http://www.trailhiker.smugmug.com/galler��
If you go to Laguna be aware that all of the tide pools inside the city limits are within a State Marine Conservation Area. This means that nothing is allowed to leave these areas, including game fish, dead or alive invertebrates, sand, rocks or shells.In case you don t already know, here are some good tide-pooler rules in general:Never remove animals, shells or rocks from tide pools.Never pick up animals. Observe them where they are.Never turn over rocks.Always walk gently, taking care not to step on plants or animals.Always remove any trash from the tide pools