The waters of Maine present opportunities for scuba divers, but also challenges. We don’t normally get the roaring surf like you might off a California beach, where the waves thunder down upon the sands. Some of those dive entry sites out west require you to literally sprint into the water between the crashing waves. All this with your gear on. Can sure make entries and exits exciting.

But a wave does not have to be huge to make it difficult for a scuba diver, especially upon entering the water. Sometimes even a dinky wave can catch you while you are sitting in shallow water putting on your fins or adjusting your mask. It can come unexpected and knock you off balance. This is called turning turtle. Much like what happens with a real turtle, it can be challenging flipped onto your back with tank holding you down, flailing around in a foot or two of sea water. Wicked embarrassing, but it does happen.

When we go boat diving, we tend to descend and ascend on the vessel’s anchor line. You roll off the side into the water and then everyone meets forward, up at the anchor line. When waves are present, they can make it challenging to work your way on the surface to where everyone else has gathered. You tend to bob up and down with the waves, which can make surface propulsion difficult.

Waves can make it difficult to assemble at the bow to descend the anchor line. Here we are preparing to visit the City of Portland wreck (Photo by Charles H. Lagerbom).

Divers are taught to fully inflate buoyancy compensators upon entering the water. This gets you up higher at the surface, the best defense against waves. Nothing more irritating than a wave slapping you in the face or filling your mouth as you are situating yourself, or getting ready to descend, or trying to climb the ladder up into the boat at the end of the dive.

I have been out in pretty open water with decent wave action going. You really feel pretty small in a situation like that, bobbing up and down. In fact, it is easy to not be seen in waters like that, as you dip into the troughs between the waves. One reason we carry, on those kinds of dives, an SMB, or Surface Marker Buoy, also known as a safety sausage. You inflate the fluorescent orange or yellow tube, either orally or with your BC inflator, and it becomes a nice, tall visual marker for spotters on the boat.

Waves, waves, waves…what is it about them? People pay big bucks to live, visit or camp beside their rhythmic sounds. Surfers like them as do painters and poets. But what causes them? What is the science behind their motion? I discovered that waves are basically the result of energy passing through the water.
Waves, tides, and currents are three inter-related factors. Let’s take a look at each. One official definition of an ocean wave is “the forward movement of the ocean’s water due to oscillation of water particles by frictional drag of wind over the water’s surface.” Who’d have thought?!

In more general terms, waves are generated by surface winds blowing across a body of water. Bigger waves come from the fetch, which is determined by how far a distance winds blow across the surface. The bigger the fetch, the larger the waves. Everything from small ripples to huge tsunamis are determined by wind speed, duration, fetch, and water depth.

Wave heights are measured between their crest or peak, and their trough or lowest point.

Horizontal measurement gives you the wavelength, determined by the distance between two crests or two troughs. They travel in groups called wave trains. Waves can be any size from small trains created by a boat, known as a wake, or large as a Tsunami, oftentimes created by undersea earthquakes.

The two categories of waves are wind sea and swell. Wind sea is when the water surface is moved by the direction and strength of winds. Swell comes from past winds, usually generated a long distance from you. This is why on some calm days at the coast, big waves still roll in. Swells are basically large waves that do not break and can be any size from small ripples to huge flat-crested waves.

For wave energy, while it appears the water is moving forward, only a small amount of water is actually moving. Instead, it is the wave’s energy that is moving since water is a flexible medium for energy transfer. When waves become too high, relative to the water’s depth, the wave’s stability is undermined and the entire wave breaks and topples onto the beach, forming a breaker. This is the crashing surf that most people recognize.

Breaking waves come in different types determined by the slope of the shoreline. Steeper bottoms result in a more plunging form of wave. Then there are rogue waves which cruise the oceans and can suddenly engulf a vessel with little warning. Off Cape Horn, rogue waves have measured almost 100 feet tall!

Trying to work our way to deeper water and less surge at Rachel Carson Salt Pond.(Photo by Charles H. Lagerbom)

Southeast winds here along the coast tend to blow out many of our dive sites. This means that the winds generate too much in the way of waves, making less than ideal conditions. We went off Rachel Carson Salt Pond one time when we probably shouldn’t have. This judgement comes with experience, and we were fairly new at the time. It was sketchy with swells and surge constantly pushing us back or hurtling us forward. We clung and moved from rock to rock but still took a decent beating trying to work our way out to deeper water, where surge conditions tend to be less. No luck. It was no fun getting pushed around by the water, so we thumbed the dive and decided to go over to Pemaquid Beach instead. It faced in a different direction and conditions off the little beach at Fish Point were way better.

Southeast winds also tend to muck up a site’s visibility. The choppy waves actually stir the water column which tends to hang more debris or sediments in the water, making viz shrink to nothing. This also occurs after area rainstorms; the runoff tends to bring more sediment and materials into the water, slashing visibility.

Smoother conditions off Fish Point beach at Pemaquid form southeast winds as opposed to over at Rachel Carson Salt Pond. (Photo by Charles H. Lagerbom)

On my check-out dive off Bay Side, we went in on a nice day, but it had rained for about two or three days before. Viz was terrible. It was so bad, our instructor broke out a length of rope with six loops on it. He then led us around as we all hung onto our loop, not seeing much at all.

The current was also not our friend that day. I remember finning along, thinking I am making decent progress. But as I’m finning, I looked down at the bottom at a large rock. I seemed glued over that rock, no matter how hard or fast I finned, the current pushing me back. This is why you should start dives up into currents when you are fresh, so that the current might bring you back at the end of the dive when you are more tired.

Preparing for our checkout dive at Bayside, conditions necessitated loops on a rope for us to be led around the site due to currents and poor visibility. (From collection of Charles H. Lagerbom)

Which brings us to the other phase of underwater challenges for scuba divers. And that is the discussion of currents!

Charles Lagerbom teaches AP US History at Belfast Area High School and lives in Northport.  He is author of “Whaling in Maine” and “Maine to Cape Horn,” available through

filed under: