Hi!
We just got back from Disney about a week ago, and we already miss it
Since DS and I were tagging along on a business trip of DH's, we decided to take a day trip to the beach. We booked the OC Beach Bus Tour, which was fabulous. They pick you up in a "woody" bus, and the driver gives you a bit of history as you cruise along. It stops in Huntington, Newport/Balboa and Laguna Beach. We spent the morning at Balboa which was lots of fun. We took a harbor cruise to check out the seals, rented bikes to cruise along the boardwalk and ate a great lunch. My DS was VERY envious of the primary school that was literally on the beach

There is a beach across the harbor (I think the town was Corona del Mar, or something like that) that had a beach called "pirate's cove". That was amazing. It's basically a little sliver of the most amazing beach on the harbor.
Then the bus came to pick us up and we went to Laguna Beach. This was probably our favorite. The scenery was amazing and they have lots of tide pools with all sorts of cool stuff in them. It's a protected marine area, so you can't take any new friends home with you. My DS (age 9) LOVED it there. He went from the tide pools to the waves and back again. They have a main beach, and then lots of little secluded beachs. The town has a free bus to get you around once there.
My vote for strictly a beach day would be Laguna. If you want to do boardwalk stuff too I would head to Newport. I also highly recommend the beach tour. It was nice not having to deal with the driving and parking
Oh - we're on the Jersey Shore, and water temp felt about the same - mid to high 60's.
ENJOY!!!!