Tips for beach vaca with baby

Has anyone traveled yet? I’m from Wisconsin and we’re taking our will-be-4 month old son to Florida next month. Any tips for the flight, pool, beach or travel in general? I’d love info on keeping him calm/entertained for the flight, what to dress him in while swimming, how to avoid a sandy mess at the beach, and any other wisdom you’re willing to share for a winter baby heading into the sun and heat. We’re hoping for as much relaxation as a baby allows so your help is appreciated 😘