Life jacket recommended for a 3yo?

Has anyone used this or have something else you recommend for a 3yo? We’re going to Hawaii and we’ll be spending every day at the beach and pool, so I want something that isn’t too bulky because my son absolutely hates extra bulky inconvenient items that slow him down (ie he’ll scream and put up quite a fight), but it needs to be coast guard approved because the ocean can be unpredictable. Please give your pool and ocean recommendations!