We've been printing for Australian customers long enough to know what works on a singlet worn in serious heat. The prints stay bright after salt water, sunscreen, and a dozen washes. We use inks that bond to the fabric rather than sitting on top of it, so you don't get that cracked, peeling look after a few trips to the beach.
We're also a clothing store that actually knows beach apparel. We're not guessing at which fabrics breathe in humidity or which cuts people actually wear at the water's edge. You get advice from people who handle this product every week, not just someone uploading your file and hoping for the best.