If you're planning to snorkel, don't just settle for a snorkel set bought off the peg without even the opportunity to try on the fins and mask for size. The only advantage of such kits is that the individual items will be colour coordinated.
Fins for snorkelling don't have to cost a lot of money. Pete Atkinson, an Australian underwater photographer, decided that he's had enough of expensive, gimmicky fins at his local dive store and went instead to his local sporting goods store where he purchased a traditional pair of full-foot fins for about US$30:
My favourite kit - Pete Atkinson - Divernet
You can get a pair like Pete Atkinson's in the USA for the same price online at
Eyeline Swim Fins
where they're sold in no less than eleven different foot sizes, from 11-1 (child) to 18-19 (adult). One of my most memorable experiences as a snorkeller of more than fifty years' standing is snorkeling at La Jolla Cove in Southern California, where I observed snorkellers shod with every kind of fin possible: open-heel bodyboarding fins; plastic-bladed full-foot fins; all-rubber swim training full-foot fins; open-heel scuba fins; long-bladed freediving fins. The common factor was their enjoyment of what they were doing. When purchasing fins, the primary criterion is sizing. Fin foot pockets have to fit not only length-wise, but also width-wise and in terms of arch height. Too tight a fit and you will get foot cramps. Too loose and you will get blisters or the fins will fall off in choppy waters. Fins are worn for power, manoeuvrability and endurance, not for speed and they must match your swimming style and strength, so it's worth borrowing different kinds to see which type suits you best. Be sceptical if somebody recommends only one make or model of fin that suits them. Whatever fins you eventually choose must fit and suit you, nobody else.
In the case of snorkelling masks, be sure to try them on before purchase. I happen to prefer traditional oval masks, but that's neither here nor there. Check each mask for fit by pressing it lightly against your face without attaching the strap and see how well it remains in place when you create a slight vacuum by breathing in through your nose. Don't believe people who say that such and such a mask will fit everybody, it's just not true and a leaky mask can be a miserable distraction when snorkelling. As for snorkels, opinion is divided when it comes to deciding between a plain J-shaped breathing tube and a so-called dry or semi-dry snorkel with valves. If you get the chance, try both and see which you prefer.