Just to give you a few sun protection advice for your snorkelling sessions.
When practising, the UV exposure is significant and can even be increased by certain factors:
The first of those factors is the "Magnifying effect" generated by the thin layer of water between your back and the surface of the water. It will increase the power of the UVs.
It is essential to know and remember than the sun's UV are still effective in water down to 25 cm, snorkelling adepts are exposed to those intensified rays most of the time, don't forget to protect your back, shoulders and thighs.
Water's cooling properties
The other danger is the fact that the water cools our bodies down more quickly and we will be less sensible to UV rays. We are then less aware of the sun's influence on our body and without sun protection, it will lead directly to sunburns...
It is therefore essential to protect your shoulders and your back. To do so, the most effective sun protection will be an anti-UV top, a neoprene top or shorty (the neoprene is a really efficient thermal and sun protection).
A water-resistant sun cream is a great addition to your snorkelling equipment. Just remember to repeat its application, even a water-resistant cream will fade faster in water.