Remembrances of beloved offshore cruiser Bruce Kessler continue to pour in following his death at age 88 in April. Kessler was among the first people to circumnavigate aboard a powerboat, helping to create the thriving community of offshore power cruisers that exists today. His 70-foot Delta Zopilote was famous in her own right, which is why boaters can’t help but recall her death, too.
It happened in 1994, after Zopilote struck what was sometimes described as an underwater seamount in Alaska. The crash left Kessler and his crew of four rushing to launch the life raft. Nobody was injured or lost, but Zopilote sank in minutes, proving just how dangerous uncharted hazards can be to even the most experienced boaters.
“As long as there have been boats, there have been crashes into submerged features, whether they’re seamounts or just part of the continent that are out of sight,” says Peter Auster, senior research scientist at Mystic Aquarium and research professor emeritus of marine sciences at UConn. “There are plenty of places that have not been charted in great detail. It would be easy to miss a narrow, shallow peak somewhere.”
A seamount is a particular type of hazard. Generally speaking, seamounts are extinct volcanoes. If they stay below the water’s surface, they’re considered an underwater seamount. If they get big enough to break through, they’re a volcanic island. According to the Woods Hole Oceanographic Institution, the highest mountain on Earth is actually a seamount. Hawaii’s Mauna Kea is more than 30,000 feet tall when measured from its base on the seafloor, 18,000 feet beneath the surface.
Researchers are still trying to figure out where all the underwater seamounts are. Some of the locations are widely known, particularly by anglers, since seamounts can be teeming with marine life. In Costa Rica, for example, there’s a seamount fishing season. From May to November, the nutrient upwelling is at its peak, attracting all kinds of species.
But even in waters where that kind of activity is already happening, we still don’t know where all of the seamounts are. This past February, the team aboard a Schmidt Ocean Institute research vessel discovered four seamounts—one that was more than a mile and a half tall—while transiting from Golfito, Costa Rica, to Valparaiso, Chile. Just a few months before that, the same team discovered one that was more than 5,200 feet tall, in international waters off Guatemala.
Researchers used those discoveries to make clear just how little we still know about what lies beneath the surface around much of the planet.
“These incredible discoveries by Schmidt Ocean Institute underscore the importance of a complete map of the seabed in our quest for understanding Earth’s final frontier,” said Jamie McMichael-Phillips, project director of Seabed 2030, which is trying to accelerate ocean-mapping efforts. “With 75 percent of the ocean still to be mapped, there is much to be uncovered.” Auster says there are probably more than 14,000 seamounts globally.
“We’ve got a satellite that can measure the altitude of the sea surface. If you map the sea surface based on the center point of the Earth, or from a fixed altitude above it, you would see that the ocean is lumpy,” he says. “Depending on how much seafloor there is beneath it, and the depth of the water, gravity affects the sea surface height. You can make assumptions about how much mass of the Earth is under the surface, and you can infer that there are seamounts in some places.”
In other words, researchers can figure out where the big mass of an underwater seamount is, but they are not yet mapping the mounts with the kind of detail that would give boaters precise information about the most dangerous spots to avoid.
Being able to spot the peaks of seamounts—along with coral, icebergs, whales and anything else around the boat that could be a collision hazard—is why an increasing number of offshore cruising powerboat owners are installing the kind of helm equipment that previously was the domain of superyachts and research, military and survey vessels, says Matthew Zimmerman, CEO at FarSounder. The company was founded in 2001, but only recently started to work with owner-operator cruisers.
“(Our equipment) has been installed now on boats as small as 58 feet—Kadey-Krogens, a bunch of Nordhavns. We’re doing our first Fleming this summer,” Zimmerman says.
The tech that those boaters are installing is FarSounder’s Argos 350, which can detect objects in the water column more than 1,100 feet ahead. The sonar also looks to port and starboard, as well as below the hull, Zimmerman says. It works at speeds as fast as 18 knots, which suits most trawler yacht owners just fine.
“Being able to give them added peace of mind, we can do that in places they don’t know, like the coast of Maine,” Zimmerman says. “Even the Bahamas—the charts there are close to useless. Once you get out of the main transit lanes, going to those little lagoons, the smaller islands, there’s really no reliable chart data.”
Every bit helps, Auster says, but there’s no need to panic when it comes to seamounts in particular. Recreational boats, even in remote and poorly charted regions, are more likely to have a problem with something like a bilge pump failure or whale encounter.
“There are boats that sink for plenty of other reasons. I’d be more worried about that than running into a seamount,” Auster says. “Try not to hit them, but realize that this hardly ever happens. There’s more things to worry about at sea when you’re on a boat.”
This article was originally published in the July 2024 issue.
