DEET.

You can fool around with all sorts of other stuff and in low stress situations they might be adequate but when you need to have something that works DEET is what you want.

Reading a beach novel you can try Skin-so-soft or bay leaves or peppermint or garlic or permethrin or what have you but for the BOB DEET is the way to go. I use 100% DEET but if your sensitive, or are using it on young children, you can use lesser percentage but your going to need to apply it more often to get the same protection.

You might also look into light-weight, compact head nets. Some go for just a few dollars. Worn over a hat they provide near 100% protection for the whole head. Keeping the critters far enough away that they aren't annoying. Something even pure DEET can't do.