School of the baby fish
Get a dry snorkel. Spend a bit more and rent a dry snorkel, or at the least, a snorkel with a splash guard. One of the least pleasant experiences is having a flood of water come down your snorkel. A dry snorkel has a special valve on top that seals shut when your snorkel goes underwater (like with a wave, or when you tilt your head to the side). It will also have a special purge valve at the bottom of the snorkel so that it is easy to blow water out of the tube. For a first time snorkeler we find this piece of equipment essential (we use them ourselves). It is worth whatever additional rental costs.