Being able to get a sense for the ocean snorkeling conditions, before you get in the water, and while you are snorkeling is an essential skill for safety, and enjoyment.
Before every snorkel we take a very careful look at the ocean snorkeling conditions, trying to see what size waves, surge, ocean currents and wind is present. If it does not feel safe, we don't push it. We just don't get in. If things look OK, once in the water we still constantly maintain an awareness of our surroundings and the conditions.
So here are some tips to help you with reading ocean snorkeling conditions. Ultimately experience is going to be your greatest aid to this, but there are some techniques we can help you with.
Getting into and out of the water is the point at which you are probably at most risk to injury. If the water is super calm and clear and there is a nice soft sandy bottom, then there is no problem. But if there are rocks, waves coming in, and not the best visibility, then you have to take much greater care.
First, the best suggestion is that if there are waves of much size at all, don't go out. It might be possible to get in and out without getting hurt, but snorkeling in wavy conditions is just not very fun. You get bounced around, it is more difficult to swim in, and the underwater visibility almost always becomes greatly reduced. If you can't see anything, what are you out there for?
Also, there is always the chance that conditions will worsen while you are snorkeling, making getting out much more dangerous.
Now if you are going out or in when it's wavy, know that waves come in sets. There is often a pattern to them. Watch carefully for awhile, before entering or exiting. Use this to your advantage. You may have three big waves, and then three smaller ones. Or a big one, and three little ones, and then a big one. Once you get a sense for the pattern of the wave sets you can enter or exit the water quickly during a smaller wave set.
Of all the ocean snorkeling conditions, currents are maybe the most important to be aware of.
The ocean flows like a river. This flow is called current, and it is different than waves, and can be moving in the opposite direction to waves. More often than not, there will be some current. Currents can be caused by many different things: tidal, wind-wave currents, reef currents, etc.
It is very important for you to be constantly aware if you are being pulled by any ocean currents one direction or another. Even a minor ocean current that you are swimming with on the way out, will make it much harder to swim back. And it is entirely possible for you to enter the water with little to no current, only to have the tide change and the current start. So you have to know if it is you moving through the water, or the water running like a river and dragging you along.
Ocean currents can move left to right along the shore, or pull you away from shore, be strong close and weak farther out, or weak close and stronger in different areas that you swim into. Once in Kauai we could hardly stand up stepping into shallow water because of a very strong left to right current, but then once we swam out a short distance over some coral, the current was much reduced.
With some experience you can start to see ocean currents from shore. And sometimes, if you know which way the current is flowing, you can enter the water upstream, and let it carry you down the beach before getting out. Then you don't have to fight it at all.
Sometimes you have to be very aware of channels in the reef that lead out to sea. The water may be entering the protected coral area on one side, and be leaving through a channel with some force. If you get caught in one of these channels that leads out to sea, you could be in big trouble. Whenever possible get local knowledge, and try to view the reef from a high area, to see where the water is flowing.
How to Know If You Are in a Current?
The easiest way to know is to stop swimming, and look down at the ocean floor. Can you detect any change in your position in relation to the non-moving ocean floor? Yes? How fast are you moving? Can you very easily swim back over the top of the point you were just looking down at? Or does it take a bit of effort to swim back or keep in the same place?
Besides just looking straight down at the bottom, we also use a method where we find a point that is close to us on the bottom, and a point farther away in a straight line. Then, if we are in a current and moving, it will quickly be clear that we are not in line with those two points anymore, indicating our direction and speed.
You can also pop your head up and pick out points in a line on land to watch. If you use this method from two different angles you will be able to tell if you are in a current, and which way you are moving. Try it right now from where you are sitting. Pick a point in the room that is 5-10 feet away, and then in a line pick a further point that is another 10 feet away. Now, move your head back and forth while looking down the line at these two points. Do you see what happens? They are no longer in line, and from this you can tell that you are moving.
Always err on the side of caution with currents. It is hard work swimming any distance through a current, and sometimes it is not even possible.
Ocean surge is somewhat like waves, except that instead of it being a wave that moves up and down, this is a much bigger motion of the ocean itself moving up and down. When you are close to shore, surge can quickly flush you in and out, despite waves not being big.
The danger with surge is when you are snorkeling over shallow areas. The wave size may be small, but surge could suddenly drop you on top of a shallow reef or other object. Because surge can come and go in long patterns don't assume that it is safe to snorkel over very shallow objects, particularly in open ocean conditions. This is also true in areas where the ocean has undercut the cliff, and you would be snorkeling under an overhang. Surge could easily lift you into the roof. Always give yourself room. And if you must cross a shallow area, do it quickly.
Like currents, wind can push you around. Be particularly wary of snorkeling in very windy conditions where the wind would push you offshore. Also know that if the tide changes, and starts moving in the opposite direction of the wind, wave size can quickly increase.
All of the ocean snorkeling conditions conditions above can change while you are snorkeling. So keep constantly aware. It does not need to be worrisome. In fact once you get in the habit of keeping these things in your awareness it requires little effort.