While this process may seem excessive, it really works and can save your snorkeling vacation. What may seem obvious to us adults, the process of snorkeling is much more complex for children and creates anxiety. It needs to be broken down into measured steps that are practiced and repeated. If you follow these steps, you'll save yourself a lot of stress and hopefully they will have an enjoyable and memorable experience.
1) Well in advance, purchase small kids mask, snorkel and short boogie board-style fins with plenty of time to ensure that they fit properly. Make sure the snorkel fits comfortably in their mouth, the mask should be snug on their face so when they breath in it sticks, and the fins should fit their feet with out falling off or being uncomfortably tight. Since kids get cold in the water very quickly, make sure to purchase a long-sleeve thick rash guard swim shirt or a thin 3mm wet suit top.
2) Start by snorkeling in a heated pool. After putting anti-fog drops in the mask and rinsing, start by having them just using the mask. Have them dive for coins or toys in shallow water. Just do this for the first couple times in the pool.
3) Next, connect the snorkel to the mask. Again in a heated-pool, support them lying flat in the pool and just have them slowly breath through the snorkel with the mask on. This process of getting them comfortable breathing through the snorkel may take 10-15 minutes. After they are comfortable, put just a little water in the snorkel and have them "blow-it-out" so they can see they can clear the snorkel. Try doing this at least a half dozen times. Then, with the snorkel in, have them go under water, pull the snorkel out and put it back in and clear it. Do this a half dozen times.
4) After a half-dozen trips to a heated pool, finally add the fins. Without a mask or snorkel, have them put the fins on while sitting on the side of the pool. When they get in, you'll need to support them level in the water and show them how to flutter kick with slow, even strokes. Children tend to kick very fast with a very bent knee. This does not work for snorkel fins. You will need to hold them level and have them "lock their knee" and move their leg for them to show them the correct slow movement from the hip. For many children, this is the toughest step of all. It may help to have them use a kick board or foam "noodle" under their arm pits while they practice slow flutter kicking from the hip and not the knee.
5) Once at the ocean, you'll need to repeat steps 2-4 again, but it can be done over the course of a day. This is best done in a protected cove where they can look for crabs or urchins in a shallow cove without wave action. Whatever you do, do not start with a boat snorkel tour since the water will be deeper, colder and have more surf. If the conditions are not ideal, don't go out and create a bad experience that might be tough to recover from. If you are heading out on a boat trip, again if the surf is too much, have them stay on board or just swim briefly instead of snorkel. Try introducing usage of an inflatable dive life-vest and a foam noodle under the arms.
6) After they are comfortable breathing and floating, you could incorporate a wristband fish ID card so they can float and look-up the types of fish they are seeing.
7) Once they are ready to snorkel on their own without your immediate supervision, try giving them a waterproof camera with float wristband so they can record their adventure (and, you'll have some time to peacefully explore on your own!).