Having lived in FL and Hawaii and currently in Cali I would have to agree that California beaches suck.
Sorry to Californians. The water is super cold, the sand is granular, the waves are rough, it’s usually dirty (i’ve seen the weirdest things on completely desolate beaches), it’s windy. It’s nice to walk or jog (with a jacket on) for maybe 20 minutes and I’m done. I like to surf/snorkel but wet suits and great whites aren’t my thing. Someone got eaten a month after we moved here.
Florida beaches are much nicer. The sand is like sugar, the gulf is nice and warm and calm, and you won’t have to deal with pollution. Summer is too hot. The spring is really nice and September-ish. Winter can be cold. Fishing, boating, jet skis, etc are great but snorkeling isn’t. The panhandle (Panama City area), the west coast (Siesta Key) are really nice. The east coast has bluer water, cooler, but the sand isn’t as nice. Miami is fun and the sand is imported but it can get pricey there. I really enjoy Miami due to the food, culture, nightlife, and beaches. Other beach towns are very sleepy. The Keys have no beaches to speak of. They’re pretty boring unless you have access to a boat for fishing / scuba / snorkeling (awesome).
That said, Hawaii is the ultimate winner for me as far as beaches in the US. There is a beach for everyone – sleepy bays, beginnner waves, reef snorkeling, fishing trips, mountain hikes, every kind of entertainment you can imagine, beautiful resorts, great food, warm water, etc etc. If you want more action it’s Oahu, less so then Maui, old school Hawaii then Kauai or big island. You could do them all really.
Another option is Puerto Rico. It’s still in the US with great beaches, sand , etc. it has great culture and food to enjoy as well as resorts. Without the safety issues of some other islands down there. It’s the Hawaii of the Caribbean.