The fresh water environment of the Seaway Trail’s waterways provide some of the best scuba diving opportunities in the world. The cool, fresh water preserves centuries-old ships and artifacts, especially those made of wood, that would have long since perished in the warmer salty oceans. Divers frequently observe deadeyes, dishes, tools, belaying pins, shoes, pottery, pumps, deckhouses, boilers, engines, winches, anchors and a variety of other remains of shipboard life. Wooden schooners from the 1800s in deep water often remain intact and appear almost as they did they day they went down!
Water temperatures vary from location to location and with the seasons. During summertime, water temperatures in the lakes can range from the low 70s Fahrenheit in shallow water to the high 30s Fahrenheit at depths below 100 feet. Mid water temperature can vary between these extremes depending on the depth of thermoclines. Thermoclines are layers of water of different temperatures, which change their depths throughout the year. Thermoclines can change the water temperature dramatically within a few feet and make the water appear to shimmer. Sometimes in late summer, the lakes can “turn over,” or flip their thermoclines, bringing the cold bottom water to the surface. This exchange can sometimes create strong temporary currents. The rivers seldom have thermoclines within the sport diving limits of 130 feet. It is common to find a uniform temperature throughout the water column, which warms and cools with the seasons. Winter water temperatures stay above freezing, but the lakes do sometimes freeze over their top layer.
Like temperature, visibility varies by location and season. Visibility is usually best in the spring and fall, and can range from 40 to over 100 feet in natural light, depending on depth and water movement. Sediment flows in and near rivers and streams, and algae blooms in mid-summer, can reduce visibility to a few feet.
A surprising variety of wildlife can be found around Great Lakes shipwrecks sites. Many fish species congregate around bottom structure, a feature lacking in most areas of Lakes Erie and Ontario. Shipwrecks and other man-made object provide the shelter and habitat these species prefer. At the right time of day (usually mornings and evenings) whole schools of panfish, such as small and large-mouth bass, perch, and sunfish, can often be found swarming like a cloud of bees around a wreck. For this reason, Great Lakes anglers often have shipwreck locations saved into their GPS and Loran units. Other fish species that make wrecks their home include muskellunge, northern pike, carp, sucker, freshwater drum, and eels. The latter can sometimes be seen sleeping under overhangs during the day, and drifting vertically like ribbons during night dives.
Shipwrecks and the lakes’ rocky geologic features left behind by glaciers are also the home of many invertebrates, including the freshwater sponge and the zebra and quagga mussels. Freshwater sponge are pale in color and grow on hard substrates such as rock, metal and wood. They grow in a variety of shapes which lack symmetry. Recent studies suggest the growth of sponges is becoming so prolific they can overspread zebra mussel colonies, killing the stripped mollusks. The zebra and quagga mussels are a non-native species that entered the Great Lakes from the ballasts of vessels from Europe. Both mussels carpet rock, wood and metal surfaces, sometimes in layers several inches thick, and have been known to clog water intakes. The mussels attach themselves to shipwrecks and other structures using tiny bissel threads, and filter the water for food.
For more about the wildlife and geology of the Great Lakes, visit these web sites…