Who's been biting me all over my body?

For the past several days, I’ve had little itchy bites all over my body. I can’t tell if there are new ones coming out or if they all came at once. They are not big welts like mosquito bites. I was at the beach on Friday and a friend’s pool over the weekend. Sand fleas? Fleas (but no animals have been in my house.)? Not bed bugs are they?

They really itch and are mainly on my back and legs which makes me think they came when I was in a bathing suit. Help me!