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Running Aground Claims Analysis


With the luxury of hindsight afforded us by the last five years of marine insurance claims files, here’s the skinny on how groundings happen so you can stay out of the statistics.

It’s been said that there are two types of sailors; those who have run aground and those who lie about it. According to an analysis of BoatUS Marine Insurance claims files, there’s a whole bunch of powerboaters who run aground as well. We may not be able to tell who is fibbing, but we can tell you which boats run aground, where, when, and how, and tell you how to avoid being a statistic in our next grounding analysis.

Running aground can be as simple as, “oops, we’re stuck,” to “all hands on deck and start bailing!” The primary factors that separate the two are speed of the boat and hardness of the bottom. For our purposes, we’re talking about a grounding that stops the boat’s progress. As you can imagine, how fast that happens makes all the difference. A gentle slow-down into the pudding-like muck in parts of Chesapeake Bay usually causes little damage (though mud sucked into the engine’s cooling water intake can overheat the engine), while a direct strike at speed on a rock ledge in Puget Sound or Lake Michigan will almost certainly entail some broken pieces.


Big boats draw more water and often go faster, so you’d expect them to run aground more often. And you’d be right. In fact, boats over 27 feet long are more than twice as likely to be grounded than those between 23 and 27 feet. Big boats are heavier, too, which means two things here: They’re more heavily damaged and they’re harder to get free. Repairs, on average, are more than twice as expensive in the big boat group than the next smaller group. Many of the big boats have twin engines, and the cost of rescuing those boats is often much higher. On the other hand, bigger boats usually have more sophisticated electronics, which means that a competent operator should be able to steer clear of obstructions. That means knowing how to use them and paying attention to them without ignoring your surroundings.

Types Of Boats

If we told you sailboats were far more likely to run aground, you’d probably think, well, yeah. It doesn’t take a rocket scientist to understand that if you have a boat that draws 5 feet of water, it’s way more likely to run aground than one that draws only 3 feet. But before all of you powerboaters start patting yourselves on the back, notice that trawlers come in tied for second with multihull sailboats. It’s also probably no surprise to learn that with that big, deep keel underneath, sailboats experience more expensive damage.

Drive Type

Inboards rule here, which is no surprise because most sailboats and trawlers (the most well-represented groups) have inboard engines. Pod drives seem high, but it’s due to the fact that there are so few in the study that it takes very few claims to push them near the top. Unfortunately, when pod drives run aground, their repair costs are higher than any other type. In many cases, pods are simply torn off (they’re designed to break away, leaving the boat sealed from the water to prevent it from sinking after a major strike), but they’re much more expensive to replace than other types of propulsion.


So where do most of the groundings occur? Michigan has the dubious honor of coming in first place. There are a lot of hard bottoms in Lake Michigan, and boaters seem to run aground on them regularly. This probably has a lot to do with lake levels. Our study goes back five years, when both Lake Michigan and Lake Huron were 2 feet below average, which of course meant that the rocky bottom was 2 feet closer to a boat’s hull.

It pays to check the water level in large and small lakes before going out. That goes for boaters in New York, too, who have the second-highest grounding rate. Most New York groundings happen in the ocean, which means a simple check of the tide chart will let you know when water levels are low.


Summertime is when boaters need to be most wary, according to the statistics. But spring (May) and fall (September) are also busy months for groundings. In spring, navigation skills may be a little rusty, and in fall, complacency begins to settle in. In the summer, obviously more boaters are on the water, but also the sun is high in the sky and can hide shallows and ledges (and even some onboard displays), so be extra vigilant and slow down if the sun is obscuring your view.

Analyzing statistics is helpful for understanding how grounding claims happen. The takeaway, though, is how to avoid them. Knowing the waters (and depths) you boat on, being vigilant with depth sounders and other electronic aids, and simply paying attention to where you are — and slowing down if you don’t know — is the best way to avoid a grounding and prevent yourself from becoming a statistic.

Charles Fort

Contributing Editor, BoatUS Magazine