Keep in mind that the airlines are still stuck on those 3 oz. bottles of stuff, so giving people travel sized products is a welcome relief from the pouring and concocting into little bottles (which don't work well, and are a nightmare to clean out).
First, a good cleanser. Yes to Carrots makes a great, paraben free exfoliating one that'll scrub off all that sunscreen and sand without poisoning the environment. It smells good and works well.
Second, a great moisturizer. Look no further than Dr. Hauschka Rose Day Cream. Yes, it seems all sticky and heavy, but nothing protects and nourishes quite like it. It smells lovely (without artificial fragrances), gives that youthful dewy glow, and lasts forever. It's also perfect for those harsh dry plane climates.
Of course, there's also the dry skin everywhere besides the face to contend with, and Weleda's Skin Food does the job. It's another "green" product, it's thick and comforting, and it banishes lizard skin (elbows and knees, anyone?) in an instant. Plus, it's thick enough that there's no nasty leakage issues to worry about.
And how about hair? While I'm in favor of simply buying shampoo and conditioner once you've landed, I do find this Oscar Blandi dry spray shampoo to be a godsend. It just kills the grease dead, and adds a ton of body, too. But if deep conditioning in the tropics is a priority, pick Weleda Rosemary Hair Oil too. It's good to have options.
So, that's the Best Travel Survival Kit I can come up with for a beach vacation (although it's really awesome for any type of vacation, anywhere. And you can find all these products, every last one, at 3 Fluid Oz.