WebMD agrees: Above SPF 15 is a waste, and definitely get protection from UVA.

So which is the best sunscreen for you? Clearly, you'll want a sunscreen with broad-spectrum or multi-spectrum protection for both UVB and UVA. Ingredients with broad-spectrum protection include benzophenones (oxybenzone), cinnamates (octylmethyl cinnamate and cinoxate), sulisobenzone, salicylates, titanium dioxide, zinc oxide, avobenzone (Parsol 1789) and ecamsule (Mexoryl SX).

• SPF 15 or higher for UVB protection. The SPF factor rates how effective the sunscreen is in preventing sunburn caused by UVB rays. If you'd normally burn in 10 minutes, SPF 15 multiplies that by a factor of 15, meaning you could go 150 minutes before burning.For the vast majority of people, SPF 15 is fine, Leffell tells WebMD. But people who have very fair skin, a family history of skin cancer, or conditions like lupus that increase sensitivity to sunlight should consider SPF 30 or higher.Keep in mind that the higher the SPF, the smaller the increased benefit: contrary to what you might think, SPF 30 isn't twice as strong as SPF 15. While SPF 15 filters out 93% of UVB, SPF 30 filters out 97%, only a slight improvement.
• UVA protection. There is no rating to tell you how good a sunscreen is at blocking UVA rays, says Leffell. So when it comes to UVA protection, you need to pay attention to the ingredients.Look for a sunscreen that contains at least one of the following, Leffell says: ecamsule,avobenzone, oxybenzone, titanium dioxide, sulisobenzone, or zinc oxide. Any of those should do the trick.
• Ecamsule. One newly approved ingredient that blocks UVA is ecamsule. It's been available in Europe and Canada, as Mexoryl SX, since 1993. In the U.S., ecamsule is now sold in L'Oreal's Anthelios SX products. It isn't cheap. A 3.4 ounce tube -- barely enough for 4 full-body applications -- can run $30.
• Avobenzone. Neutrogena's Helioplex isn't really a new ingredient; it's a "stabilized" version of a common UVA-blocker called avobenzone (or Parsol 1789). Unless it's stabilized, avobenzone breaks down when exposed to sunlight -- exactly what youdon't want in a sunscreen. You'll find stabilized avobenzone in other sunscreens, too, like Active Photo Barrier Complex and Dermaplex.Some of the excitement about these new products is advertising hype, says Leffell. For instance, any brand-name sunscreen that has avobenzone is stabilized. If you want to spend $30 on a bottle of sunscreen, go ahead. But you can get equally good protection for a lot less.
• Titanium dioxide or zinc oxide. Less expensive options for UVA protection have been available for a long time, the experts tell WebMD. Old sunscreens with titanium dioxide or zinc oxide used to make people look pale and ghostly, says Fairbrother. But newer manufacturing techniques have resolved the problem, she says.
• Water and sweat resistance. If you're going to be exercising or in the water, it's worth getting a sunscreen resistant to water and sweat.But understand what this really means. The FDA defines water resistant sunscreen as meaning that the SPF level stays effective after 40 minutes in the water. Very water resistant means it holds after 80 minutes of swimming. These sunscreens are in no way water-proof, so you'll need to reapply them regularly if you're taking a dip.
• A brand you like. Even if a brand is recommended by all the experts, if you don't like it, you're not going to use it, says Karrie Fairbrother, RN, president-elect of the Dermatology Nurses Association. Personal preference is really important.
• Kid-friendly sunscreen. The sensitive skin of babies and children is easily irritated by chemicals in adult sunscreens, so avoid sunscreens with para-aminobenzoic acid (PABA) and benzephenones like dioxybenzone, oxybenzone, or sulisobenzone. Children's sunscreens use ingredients less likely to irritate the skin, like titanium dioxide and zinc oxide. Unlike chemical ingredients, these protect babies' skin without being absorbed, Fairbrother says.For kids 6 months or older, look for a sunscreen designed for children with an SPF of 15 or higher. The American Academy of Pediatrics recommends that babies under 6 months be kept out of the sun altogether.

Source: http://www.webmd.com/beauty/sun/whats-best-sunscreen

As a former lifeguard who had to work all day in the sun for 80 hours a week, liberal use of SPF 50, re-applied every hour when it came out was a godsend. 

For someone in the sun that much it makes sense.