Sometimes during a dive, conditions are just perfect. Sun is warm, sky is clear, sea is calm. Other times, not so much. Then what?
First, just to make sure there are no misunderstandings: diving should be both fun and safe. If you’re ever in doubt as to whether a dive will be either, due to rough conditions, always err on the side of conservatism and cancel the dive. Never dive in a situation where you feel you’re outside of your dive skill range.
That being said, as you increase dive experience, the definition on non-divable conditions will change, as your increased skill and experience will make it possible for you to dive in conditions a newbie would not. To make diving safe in situations where the conditions are less than optimal, there are a few precautions you can take.
Check with locals before diving
If the conditions are rough, the first thing you should do, unless you know your dive very, very well. Is to check with local divers and dive shops to get an idea of what conditions you can expect.
One thing is what the conditions are above the surface, but what you need to find out is what to expect below. Some places are less susceptible to rough conditions, and while the surface may see waves and strong wind, the dive site can be perfectly tranquil at only a few feet of water.
So find out by consulting the locals. What will it likely be like out there? Currents? Swells? When is the area non-diveable? What are you backup and exit options? If in doubt, ask a local divemaster to join you as a precaution.
Getting into the water
The basic strategy here is to get in the water and below the surface as fast as reasonably possible. Waves only have effect at a depth equal to roughly twice their own height. So descending below this will make things much calmer.
If you are diving from shore entering the water when there are large swells can be tricky, but there is a technique that can make it easier. Buddy up in pairs (use you pre-defined buddy pairs). Stand side by side and place a hand on each other’s shoulders to help stabilize each other. Put on your dive mask and regulator. Then start walking out.
Time your movements so that you walk when the water is out, and stand your ground when the waves are rushing in and out. As you get closer to deep water, around mid-thigh height, turn around so you’re facing the beach and walk out backwards, still holding on to each other.
As you get into ever deeper water, try to time it so that you jump slightly when the waves come in, to keep you head above water. Continue out until you reach beyond the surf zone where the waves are generally milder. Here, you put on your fins and descend.
Diving from a boat, you’ll want to try and exit the boat when a wave is upon it, to reduce how far you need to jump (if doing a giant stride) or roll (if you’re doing back-roll entry). Then deflate your BCD and descend as quickly as possible, regrouping with your buddy once you’re about 15 feet down, or below the effect of the waves.
If you’re comfortable with it, try doing a negative entry, where you jump in with a completely deflated BCD and start your descent as soon as you hit the water.
Once diving the rough sea
If you descend and find that conditions at your dive site are worse than expected, abort the dive and head out of the water. Always bring a DSMB if you’re diving from a boat. Make sure you know how to use your DSMB.
But often, you’ll find that as you descend, the water becomes calmer and the visibility better. Complete your dive, and do a safety stop.
Exiting after the dive
When you exit, the same rule applies as when entering, but in reverse. That means that your goal is to spend as little time as possible bopping up and down in the surface.
If you’re exiting on shore, you will start to feel the surge of the waves more and more as you reach shallower water. Don’t fight this, but rather, as the surge is against you, fin lightly, just enough to stay in place. If possible holding on to a rock or similar to help, and then, when the surge shifts, kick hard and pull yourself towards shore, assisted by the surge.
When you just outside of the surf zone, surface, remove your fins and approach the beach using the same technique as when going out.
For boats, time your climb with the waves, using the crest of a wave to assist you in climbing up.
Final words of diving in high sea
Again, it is worth repeating that diving in rough conditions should only be done by divers with sufficient skills and experience You should always cancel a dive rather than risking getting yourself in a situation you’re not comfortable with.
Always remember that rough sea is equal to low visibility blow and above, make sure not to get left behind here's 4 Things That Help You Not to Get Left Behind and just maybe you should consider the ultimate dive safety equipment.