For men: T-shirts by Stussy; baggy, knee-length shorts of khaki or denim; low-top sneakers (Simple, Converse and Puma are popular styles), Teva or Reef sandals. For a (slightly) dressier look, try a collared shirt in a retro print, plaid or stripe, worn outside classic baggy trousers in khaki, black or white.
For women: Men's clothing as above; flannel shirts; baseball caps; straw hats; cowrie shell necklaces; ankle bracelets; floral slip dresses; boots (yes, even at the beach, Doc Martens are in); platform and heeled clogs; strappy leather sandals; shorts and T-shirts.
Bathing suits are two-piece for fashion (although one-piece is still recommended for actual swimming), with bikinis showing a slightly lower "American" leg instead of the high-riding Brazilian cut. Although bikinis come in some retro prints and colors, bright florals and neons are still popular.
For both: Baseball hats with the brim either way; oval wraparound sunglasses in plastic or wire frames by Arnet, Oakley and (surprise!) Stussy; Teva and Reef sandals; Puma, Converse, Simple, Van or Adidas low-top tennis shoes; Doc
Martens, other heavy-looking boots.