PREPARATIONS AND PRECAUTIONS FOR DIVING IN MAINE
The Maine coast offers some of the world's most rewarding diving, but it also presents many unique or amplified hazards. Before you dive, be sure you are familiar with the general challenges you will face and the particular hazards and conditions at your dive site. Ask local dive shops any questions before diving. And please, dive within your abilities and always with others.
Water temperature. By most standards, Maine water is cold. In the spring, the short days limits the amount that the sun can heat surface waters, and the strong spring winds mix the surface well with the cold deeper water. Surface temperatures off Portland, for instance range from 39°F in April to 51°F by the end of May. The summer brings the greatest solar heating at the surface and the summer's light winds cause the least mixing. In areas unaffected by tidal mixing, this creates a realatively warm surface layer over a distinct thermocline. On average, summer surface temperatures climb from the mid 50s in June to the low 60s by the end of August. Locations with strong tidal influences, such as Jonesport, will be about 10°F colder. Autumn winds mix surface waters, dropping surface temperatures to about 50°F by late October. Jonesport, where the predominant mixing is tidal, has less autumnal variation because the tidal mixing has kept the surface temperatures cool all summer. It's surface water temperatures remain at about 50°F through October.
See current surface water temps and averages chart.
Divers need to dress for the cold water. Even taking into accoun the physiological differences, most divers will need at a minimum a full wetsuit with a hood, booties, and gloves. It is essential to have the suit well fitting in the three major heat loss areas of the body: the head and neck (60%), the inner thighs near the femoral artery, and under the arms near the brachial artery. The colder the water, the greater the heat loss. And the longer you plan to stay in the water, with multiple dives, for instance, the more chilled you will get. Typically, a 5mm (3/16") wetsuit may be adequate for shallower dives at the height of summer. Extended diving requires a 7mm (1/4") wetsuit or combinations of thinner neoprine layers, or any of the various drysuits. Farmer johns or shorties beneath jumpsuits help double the insulation over the arms and thighs. Diving off-season almost necessitates the investment of drysuit gear. Thicker wetsuits or drysuits requires more weight to neutralize your bouyancy. More weight means more to carry down the slippery rocks or onto the boat, but it beats being cold!
Water temperature in Maine affects underwater visibility in the form of algae blooms (see visibnility, below) and visibility at the surface in the form of fog. Cold surface temperatures can cool humid summer air and reduce visibility to zero. This can greatly affect a divers ability to find his boat, the shore, or his way home. See fog, below.
Tides. Maine's tides are a fact of life for diving along the coast. Divers should always know the state of the tide and how it may affect their dive.The average tidal ranges in Maine run from close to 10' in the south to over 20' in Passamaquoddy Bay. The enormous volumes of moving water associated with these tides creates strong tidal currents, particularly where water movement is constricted or diverted by landmass. In many places, this current can be stronger than any diver and may create situations where a diver might not be able to swim back to his boat or put-in or where a diver prematurely uses up his air working against the current. Even light currents can greatly increase the risk of entanglement in lobster gear or separation from buddies, because even whe the diver is at rest, he is being carried by the movement of the water.
Dives are often best planned around high or low slack water. Remember, however, that slack water at your local dive site is likely to be somewhat different than the predicitons from tide tables, due to that site's particular topography. Divers may get in the water believing it to be close to slack but discover that there is still a strong current. A dive might have to be posponed, changed, or called off. Be flexible.
Divers can also use tides to their advantage. Linear dives can be planned around slack water, either at high tide or low, so last of the tidal current can help the divers drift in one direction before the current reverses itself and helps the divers return.
Every diver should familiarize himself with the lay of the surrounding land before a dive. Be sure to look at a chart. In the event that currents prevent a diver from returning to his put-in or his boat or his diver group, he should lknow whether the current will take him toward land or away from it, and to act accordingly. If the current will take the diver toward land, it may be safest to drift to the land and get out of the water. If the current is heading away from land, it may be best to swim at an angle to the currrent to ferry toward a shore. The more these situations can be anticipated and discussed before a dive, the better.
Visibility. Generally, underwater visibility is best in colder water, which limits blooms of plankton. But even in summer, Maine has no shortage of cold water. Inner bodies of water such as cove and harbors are warm and murky, you can often move to more open areas and find clearer water.
Fog. Maine's cool waters have often been called a "fog factory." When warm, moisture-laden air blows across the cold surface water, the moisture in the sir condenses into fine droplets, forming a low cloud bank. This can happen along whole sections of the coast at once, when easterly winds bring air laden with moisture from the Gulf Stream across the colder waters in the Gulf of Maine, or it can happen locally where fog hovers over tongues of cold water. The deep, cold Sheepscot River is a good example of this. On many summer days, both shores of the river's mouth will be sunny, but wall of fog will be snaking up the center of the river.
Divers should be aware of fog because it can form quickly with just a slight wind shift. Dives should be planned so that the put-in or boat or home port can be found if visiblity diminishes or disappears altogether. If the ari is moist, if fog is nearby, or if the haze of a day is thickening, be sure to surface often during a dive to assess the changing visibility and to reorient yourself.
Boats. Maine has fewer boats than anywhere else in New England, but many of those boats work harder. Lobsterboats, in particular, often are working close inshore or above underwater formations–often exactly the same places you may be diving. And the men and women at the helm are often too busy to be watching carefully for dive flags. While technically they are required to avoid your dive area, don't expect this to happen. Dive defensively. If you are about to dive and boats are working the area when you want to splash, wait. Most lobsterboats make quick work of their strings of traps and move on to the next. Also understand the hman factor here: lobstermen are understandably suspicious when they see divers near their traps. Don't give them any reason to be. Taking lobsters from a trap, or touching a trap, pot warp, or even lobster buoys is illegal and taken very seriously in Maine (see Laws and Regulations).
Recreational boats pose a similar danger but for different reasons. It is a sad fact that many recreational boaters do not know what a dive flag is or what it means. Do not expect them to see your flag or acknowldege it. Avoid diving in major thorofares. Listen carefully when underwater, particularly when ascending. Stay submerged if you hear boats nearby.
I was once diving very close to shore, towing a buoyed dive flag. Near the end of the dive I was ascending and at a depth of perhaps 20' my dive flag rope suddenly was yanked hard from my hand. I looked up and saw, directly above me, a Whaler-type hull with an outboard that was tied in knots by my flag rope. I had heard nothing. When I surfaced, though, the two operators of the boat sure heard from me! My appearance nearly gave them heart attacks. They had been trolling, barely moving, with two fishing lines (and hooks!) still in the water. When I pointed to my flag, now wound alongside their boat, they said "We thought it was a lobster buoy."
Wildlife. Few, if any, underwater creatures present dangers to divers in Maine. Sharks and sea mammals will avoid you, but you should do the same. Do not dive near seal rookeries. Lobsters do pinch (and it is illegal for divers to catch them. See Laws and Regulations.). Shellfish such as clams and mussels are affected by red tide, so if you are a forager, be sure to call the red tide hotline to confirm that the shellfish you plan to gather are not affected (More red tide info). The greatest danger from wildlife, perhaps, are the barnacles on the rocks.
Emergencies. Before diving, it is a good idea to compile emergency numbers and the location of the nearest hospitals and emergency rooms. Our list emergency services also contains the location of hyperbaric chambers in Maine, though we urgently advise going to the nearest emergency room, rather than to a hyperbaric chamber directly. Emergency rooms have greater supplies of intravenous fluids, oxygen, and medication. Physcians need to rule out numerous possible conditions or illnesses, and the location, operating hours, or status of hyperbaric chambers may change. Please see diving emergencies for more details.