The water temperature in both San Diego and Tijuana in the summertime is colder than Long Island!
I’ll take the East Coast. No earthquakes. Nowhere near a desert. And as long as you’re not in upper New England, you can go swimming in the summertime.
And if you’re further south, depending on where you are, you can swim during portions of spring and fall as well.
South Florida is the only place where you can swim all year round. But watch out for those man o’ wars and jellyfish!
Personally, my favorite Florida beaches are on the Gulf side, especially the Panhandle in the quieter spots. Hidden gems. When I say sugar white sand, I mean it.
Give a Long Island beach anytime.
California has a lot of good surfing beaches, but the Japan Current brings cold water down from Alaska, so it's not so good for swimming.