When you snorkel it is important to follow certain guidelines before you dive in. Certain checks such as, is it cold? Is there a current? Where are your buddies? Is the spot beyond your skill level? Are there any dangerous creatures? All of these questions should be answered before you get into the water.
Cold water can be very dangerous if you're not prepared. Without the proper wet suit you could possibly suffer from severe heat loss, so it is important to find out if the water temperature is right for you beforehand. Current can be very dangerous when snorkeling. Even the smallest currents can be misleading. It is important that you never allow your buddies to enter a heavy current. Evaluate anything drifting or floating around, the speed, direction, and waves before entering the water. Be aware of your buddies at all times in the water. Also before going you should contact the local dive shop about any dangerous creatures you might have to be cautious of.
When snorkeling despite all these cautions, it is important to never panic. Panic is your worst enemy under water and it is extremely important to remain calm and level headed in any emergency situation.
These are important guidelines to follow before you enter the water. Snorkeling can be very fun, but also can be dangerous if you don't follow certain guidelines such as these.