The Sea Monster That Threatened the Netherlands

On a fall day in the year 1730, in the Dutch province of Zeeland, a most vile and vicious invader was found. Had he been a lone invader he might have been subdued. Unfortunately, the villain brought reinforcements.Too many in fact, for the Dutch to fight off. Oh sure, the malefactor and his friends were small and on the surface unintimidating. They didn’t have guns, or bombs, or even bows and arrows. Heck, they didn’t even know how to make fire. What they did have was voracious appetites. In fact, it was their insatiable hunger that threatened the safety of the entire country. The tiny villain was a worm, the shipworm.

The name’s Navalis, Teredo Navalis.

Well yes, if you want to get technical that is the Latin name. No matter what you call him, the shipworm isn’t really a worm at all, he’s a saltwater clam. With a tiny shell and a long tube-like body, he’s not a pretty fellow—but what of it? He’s a villain and villains are supposed to be ugly and horrid. Cute and cuddly seldom has what it takes to induce a soul-shaking fear.

Now sailors had been acquainted with the evils of the shipworm for sometime. Just ask Christopher Columbus, Francis Drake and the Spanish Armada. They all knew that shipworms have a particular fondness for wood, especially wood soaking in salt water. They also knew finding them in the wood of your ship, spelled disaster. This is how he got the name Navalis, it’s Latin for Naval nightmare.

A dried shipworm. I told you he wasn’t cute

Dinner Served 24 Hours

To the Dutch, however, having millions of these sea monsters coming to vacation on their piles and dikes for an all-you-can-eat buffet was something new. They had dealt with floods before, including a disastrous Christmas Eve flood just 17 years earlier. However, never in their history was there a threat by anything like a worm. So when our inspector noticed part of a wave breaker broken off, he was rather shocked to see worms all snug and cozy inside the wood.

“Hey, ” he said to the worms. ” I don’t know who you are, but you’ve just made our breaker into Swiss cheese and I hate that!”

Now, it wasn’t that the inspector had anything against the Swiss, but he knew that the worm eaten wood could never stand up against the fury of the sea.

The dikes were the only thing stopping the sea from reclaiming the territory the Dutch had stolen from it, and it was a  struggle that had been going on since about 400BC. The first dikes were built to protect crops and they’ve been expanding ever since. Today about 27 percent of the Netherlands is below sea level. Despite only 880 kilometers of coastline, the network of dikes extends a whooping total of 22, 000 km. Sea defense today can be complex, but in 1730 it consisted mostly of seaweed and wood.


Windmills helped keep polders, or low-lying lands, dry. Today this is done by electric pumping stations.

Public Enemy # 1

Now government being the well oiled machine that it is, the inspectors war cry sparked immediate action.

“We will declare war on this new enemy immediately,” said the water board. “Just as soon as we get your report in triplicate, a psychiatric evaluation of the worms, and  some eyewitness statements. It is absolutely imperative that the information comes to us alphabetized, notarized, and pasteurized. Then we will turn it over to the mayor, the police chief,  the head of garbage collections, and the animal rights activist for review. After that it will be sent post-haste to sit on someone’s desk for at least three months before sending it on to the other provinces. Once they are informed they can check their own dikes and make their own reports . . .in triplicate of course. “

When the other provinces finally completed their inspections, the unwelcome visitors were found eating away at the breakwaters of dikes in Holland and Friesland. The very foundation of the country was under threat of being eaten away.

In 1733 the government was still searching for a solution.  Meanwhile, the rest of Europe was beginning to find out about the country’s bug problem. The Swiss and Germans were sure the country was on the brink of collapse. One German newspaper reported worms were eating the stones of Amsterdam’s city hall, another reported the worms as two feet long giants. These false reports were doing nothing for the Dutch economy or reputation. The government was plumb out of ideas and  kind of desperate so they decided to place an ad in the newspapers.


Holes courtesy your local shipworm population



the ad said. It also included a warning that the perfect solution would be cheap and easy. The inventors went wild.

“Just brush on my super strengthening ectoplasmic lotion and the wood will be eating the worms!”

“No no, buy my worm repelling paint.”

“Forget his paint—I’ve got a poison so strong it will kill them and their relatives . . . in China!”

“Nails, rusty nails are the way to go. It’ll give those worms the worst case of indigestion they’ve ever had. “

Ideas flew faster than rocket propelled seagulls, but still there was no viable solution.  “You’ll never find a solution, because this is a punishment from GOD and only He can end it. All we can do is pray and repent!” some said, and many people agreed.

The country had been experiencing great prosperity, could they have gotten a bit too greedy?

Too lustful?

Too prideful?

After all, this wasn’t the only problem the country had run into recently. They had large debts, a cattle plague, and the Christmas flood. Just to be safe the government called for days of prayer and fasting. Once the plague hit the Catholic communities in the southern Netherlands, they got Rome in on the act too. God was now bombarded by the Protestants and the prayers of not just Catholics, but the pope himself. God just had to listen to somebody!


The Incredulity of St. Thomas, Hendrick Terbrugghen


 Ingenuity, God or Both?

It’s possible then, that it was divine intervention that gave Pieter Straat and Pieter van der Deure the clever idea to make dikes with boulders and clay so the little buggers couldn’t get to the wood. “No food, no worms”, said Pieter and Pieter. “With our plan—and a little help from heaven—we’ll stay safe and dry for years to come.”

There was some resistance to the 2 Pieter plan.  Stone would have to be imported from Scandinavia, which didn’t make any of the budget people happy. Zeeland thought about that rusty nail idea for awhile, while Holland and Friesland decided to wait before they accepted the plan. When nothing else worked they finally had to buckle down and spend the money.

In the end, it wasn’t so bad. Those nasty sea monsters actually gave the country the kick it needed to modernize and improve their dikes and the way they were managed. Either way, they would have eventually left when the weather turned and the rains changed the saturation of salt in the water. It seems fresh water didn’t suit their fancy. It shouldn’t be surprising, bad guys never can take whats good and pure.


Notes and Source:

Navalls is Latin for naval, but not naval nightmare.

Yes, they did but an ad in the paper, however, no ectoplasmic solutions were offered.

Check out Zeeland’s Oosterscheldekering storm surge barrier here. It’s the largest barrier in the Netherlands and has gates that can open and close.

Floods, Worms, and Cattle Plague: Nature-induced Disaster at the Closing of the Dutch Golden Age, Adam Sundberg

The Rise and Decline of Dutch Technological Leadership, Karel Davids

Chambers Journal, Vol. 55


About The Author

Nicol Valentin

Nicol Valentin is a homeschooling mom of nine who loves history, fiction, and fun.


  1. April | 4th Jan 18

    I always learn the most interesting stuff on this website. This was another fascinating read!

  2. Lisa | 10th Jan 18

    I love the way you bring history to life! My kids will enjoy listening to me read this to them, thank you! It may even spark some creative history writing of their own. 😀

    • Nicol Valentin | 14th Jan 18

      Thank you so much Lisa! I do hope your kids enjoy it, it’s much easier to remember the facts when it’s fun.

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