Appreciate recommendations for something to do for half day in San-Diego. I will be spending 1/2 day in WAP with 5 yr old.
looking for recommendation for Beach, board walk type things to do.

The Zoo is always popular with the kids.
Go to Coronado and/or Mission Bay.
Sea World.

Well, I don't know what WAP is, but we took my brother's granddaughter to Coronado and she/we loved it (it was the first time she'd seen the ocean).

It takes a while to get to the Wild Animal Park. Go to Balboa Park and enjoy.

Just to be precise, the Wild Animal Park is now called the San Diego Zoo Safari Park.

Don't ask me why!

I presume from the post that you are looking to fill the rest of a day after spending 1/2 day at the Wild Animal Park / San Diego Zoo Safari Park? Its at least a half an hour or more to any beach.

I think the best beach for a 5 year old is Coronado, but that is about 45 minutes away. La Jolla Shores or Cove is good too. None have a boardwalk. For that you need to go to Pacific Beach, but that's not my first choice for a five year old.