In Part 1 of our five-part intro series, we explored what a boat’s wake actually is—the V-shaped wave trailing behind as it moves through the water. We noted how wakes can be big or small, calm or turbulent, and how they can create opportunities or cause destruction. Every vessel, from the lightest canoe to the largest tanker, leaves a wake.

Before we get into the more metaphorical interpretations of leaving a clean wake—how we interact with people, places, and the world—it’s worth taking a hard look at the literal wake cruising sailors can leave behind, even when they take great care to protect the sea that surrounds them. Because beyond an undulating wave in the water, boats can trail other, far less desirable things: plastic, sewage, chemicals, and petroleum products.

This isn’t just an abstract concern. There is nowhere on Earth that has escaped human-generated waste.

Scientists have found plastic in the stomachs of one-hundred percent (100%) of the amphipods at the very bottom of the Mariana Trench, 36,000 feet below the surface.

(These deep-sea creatures might be homely or hauntingly beautiful, depending on your tastes—but either way, they deserve better than a steady diet of microplastics.) At the opposite extreme, Mount Everest is littered with garbage and human sewage, left behind by climbers who, ironically, set out to conquer nature’s most pristine and remote landscapes. If even the highest and lowest points on Earth aren’t free from human detritus, it’s safe to say that the waters we sail are just as vulnerable.

That brings us to a framework for understanding—and mitigating—the impacts of the inevitable wake we leave behind.

Vienna with friends Amy and Jessica in the Gulf Islands of Canada, 1997

MARPOL as a Framework for Clean Wakes

The International Convention for the Prevention of Pollution from Ships (MARPOL) is a comprehensive international agreement on marine pollution. It was designed to regulate pollution from commercial ships, not private pleasure craft—but that doesn’t mean it isn’t relevant to smaller vessels. In fact, MARPOL provides a structured way to think about the various forms of pollution that all boaters, including sailors like us, must contend with.

Of its six annexes, four are directly relevant to private sailors:

· Annex I: Petroleum pollution (oil, fuel, and lubricants)

· Annex II: Chemical pollution (toxic compounds from boat maintenance)

· Annex IV: Wastewater (sewage and gray water)

· Annex V: Garbage (plastic, packaging, and other waste)

Each of these types of marine pollution requires attention if we truly want to leave a clean wake. So let’s dive into them.

Source: https://www.imo.org/en/about/Conventions/Pages/International-Convention-for-the-Prevention-of-Pollution-from-Ships-(MARPOL).aspx

Petroleum in the Wake

Nearly every boat, even a sailboat, has an auxiliary engine—meaning oil and fuel are part of the equation. Fuel tanks must be filled, engines require oil changes, and motors discharge a mix of cooling water and exhaust. Unlike filling up a car at a well-maintained gas station, sailors often deal with fuel in much messier, hands-on conditions.

We always carried a stack of oil-absorbent pads (which we called “diapers”) to wipe down the bilge, catch drips during oil changes, and mop up accidental spills. Despite our best efforts, the occasional bit of oil or diesel would still find its way into the water.

We learned that the common boater’s “trick” of squirting detergent onto a fuel spill to make it disappear is, frankly, a terrible idea. The soap doesn’t remove the oil—it just emulsifies it into tiny droplets that disperse in the water, where it remains just as toxic. And now there’s detergent in the water too, which isn’t exactly an environmental win. The only real solution? Skimming the spill with absorbent pads—a small-scale version of the skimmers deployed after major oil spills. Not fun, but necessary.

Michael, up close and personal with his beloved 1983 Perkins 62hp diesel engine. Note the USCG no discharge placard on the engine room door.
(Oil placard image source: https://www.usps.org/lc/grandlake/VSC.htm)

Chemical Contamination

Boats are floating chemistry experiments—whether we like it or not. Fiberglass hulls, epoxy resins, marine sealants, paints, and cleaning agents all contain chemicals, and they don’t always stay where we put them. (Boats, after all, are constantly trying to sink, which is why we’re always caulking, sealing, and slathering things in protective coatings.)

One of the biggest culprits? Antifouling bottom paint. This paint prevents marine growth from encrusting a boat’s hull, but traditional formulations contain copper which, by design, sloughs off into the water and accumulates in marine ecosystems. As bad as copper is, it used to be worse—tin-based bottom paints were so toxic they were eventually banned for most applications. (As far as I know, only the U.S. Navy still gets to use them. Perhaps fish salute as they swim by?)

There are now silicon-based bottom coatings that make hulls too slippery for marine life to attach, without poisoning the water. They’re not perfect, but they’re a step in the right direction.

For general maintenance, responsible sailors use biodegradable, phosphate-free cleaners—or better yet, plain vinegar and baking soda. These small choices help ensure we aren’t leaving an invisible chemical wake behind us.

The Wastewater Problem

Let’s talk about the less glamorous side of boating: sewage. A boat’s “black water” (sewage) and “gray water” (from sinks and showers) need to go somewhere.

MARPOL Annex IV lays out strict rules for commercial ships, but pleasure boats fall into a regulatory gray area. The Clean Water Act prohibits untreated sewage discharge in designated No Discharge Zones, but enforcement varies. Like RVs on shore, pleasure boats have holding tanks for wastewater. When cruising in coastal waters, responsible boaters have two options: they can pull into a marina and use its pump-out facility, or they can employ expensive high-voltage electrical systems to sanitize waste (to levels cleaner than municipal sewage plants) before pumping it overboard. When offshore, sailors can discharge waste directly into deep water, much like digging a cathole in the wilderness. All of this assumes, of course, that you have a working toilet in the boat.*

Garbage and Plastic: The Most Persistent Wake

Of all the pollutants we leave behind, plastic is the worst—because it never really goes away.

A critical fact: No petroleum-based conventional plastic biodegrades. Instead, it photodegrades, breaking into ever-smaller pieces under sunlight. Over time, it becomes microplastic, which persists in the environment forever for all practical purposes.

When cruising, the scale of the plastic problem is inescapable. Ghost nets (lost or discarded fishing gear) drift through the ocean, ensnaring marine life. Remote beaches are littered with plastic bottles, wrappers, and flip-flops—sometimes with labels from halfway across the world. Even in the open ocean, microplastics have infiltrated the marine food chain, from plankton to whales.

The best way to keep plastic out of the water? Keep it off the boat in the first place. We’d remove excess packaging before leaving port, repack food into reusable containers, and hang onto every scrap of plastic waste until we could dispose of it properly, ideally into a recycling stream—though “properly” is a loaded word, given that much of what enters the recycling stream never actually gets recycled. Even in the developing regions we visited, most marinas still had reliable systems for getting plastic to a landfill where it could be contained.

The Big Picture

As individual sailors, we can:

· Maintain our engines to prevent leaks and use oil-absorbent pads to catch oil or fuel that still manages to escape.

· Use eco-friendly (or at least friendlier) products whenever possible.

· Handle our waste responsibly.

· Reduce plastic use and keep trash out of the water.

But personal virtue will only take us so far. Large-scale problems demand large-scale solutions. MARPOL, U.S. Coast Guard regulations, and international agreements set necessary standards that help protect the marine environment. An important part of leaving a clean wake means abiding by those policies to be sure; but unless we work as policymakers ourselves, an equally important part is to lobby for change, vote for candidates who support smart policies, and hold the industries and suppliers we do business with accountable as best we can.

We’ll explore that more in a future post. But for now, let’s focus on what’s within our power—because whether on the water or in life, we all leave something behind.

Let’s make sure it’s clean.

* The Bucket Incident: A Brief (But Unpleasant) Digression

To keep a boat’s black water plumbing—including the toilet itself—free of mineral buildup, cruising sailors periodically flush the system with muriatic acid (a diluted form of hydrochloric acid, the same stuff used in swimming pools and safe when used correctly). The night before departing from Isla Mujeres for the U.S., I did just that, using acid I’d picked up at a hardware store in Mexico. Unfortunately, I misjudged the concentration and, well… overdid it.

Sometime in the middle of the night, Vienna woke me up: “Dad, the toilet is all wet.” This was not the kind of midnight news a sailor wants to hear before a multi-day ocean passage. Sure enough, the acid had cracked the toilet, leaving us without a functioning head just hours before departure. We had a limited weather window—there was no turning back. And so, we set off into rough seas… without a toilet.

That meant one thing: the bucket. Poop in bucket, dump overboard, repeat. (Many people, when imagining the cruising life, mistakenly picture white gloves bearing drinks on silver trays to lounging sailors. The reality is far less glamorous.) But wait, it gets worse. The universe, with impeccable timing, chose this moment to strike Ginny and me with a brutal case of diarrhea.

I will never forget the look Ginny gave me as she clambered up the companionway juggling a sloshing bucket of… well, you get the idea, as she made her way to the stern in a rolling sea. Gear failures, violent storms, dragging anchors… Few moments in our four years aboard were lower than that bucket brigade.

Days later, we made landfall in Key West, dropped anchor, and I made a beeline for shore. At West Marine, I arrived just as they were locking up for Memorial Day—but miracle of miracles, they had a drop-in replacement for our toilet. I installed it that evening.

Marriage saved.

Continue to Part 4