The hidden magic of the Dutch underwater world

Many divers dream of travelling to far-flung tropical destinations, but the true explorer knows that adventure is right on our own doorstep. Rob Dekker, the face behind DiveActivity, has been proving for more than twenty years that Dutch waters are teeming with biodiversity, history and pure magic. On the weekend of 6 and 7 February 2027, he will take the stage as a guest speaker at Duikvaker to share his passion. Ahead of the event, he gives us an exclusive preview of what makes our own waters so fascinating. "Once you learn to read the seasons, you see the same cycle underwater as above — just with completely different leading characters."

Rob, many divers seek adventure thousands of kilometres away, yet you make a very deliberate choice to dive in Dutch waters as well. What is that particular, intimate feeling that Dutch nature gives you the moment you slip beneath the surface?

"That feeling is a wonderful blend of pure magic and Dutch pragmatism. Diving in the Netherlands — and in the waters of Zeeland in particular — is far more diverse than most people imagine. The variety and biodiversity shift so dramatically with the seasons that there is always something completely different to see and, above all, to discover. On top of that, the practical side is simply ideal: it is literally on your doorstep. Compared with other continents, it could not be more accessible. You do not need to travel thousands of kilometres to have a truly memorable dive."

Dutch water has a reputation for being dark and cold. Yet you see pure beauty in it. Can you describe the moment you first realised that our own lakes and Zeeland are just as visually captivating as a tropical reef?

"When we first started diving, we looked at the underwater world in exactly the same way as many divers do in the tropics: straight ahead, scanning for the big creatures and sweeping landscapes. But we quickly learned that in the Netherlands you need to focus on a much smaller scale — sometimes down to a square decimetre.
Only then do you discover how much beauty is hidden there. Don't get me wrong: visibility is genuinely not always a metre or less — far from it! But much of the remarkable marine life here has simply mastered the art of camouflage. A keen eye and a solid knowledge of underwater life are real assets. It is precisely that active searching that makes a Dutch dive so endlessly fascinating to me."

With DiveActivity you often seek out quieter spots, well away from the well-known hotspots, diving in unexpected locations such as the Randmeren. Can you highlight one unique dive site for us?

"There is an explorer in all of us, and that is certainly true of our team. At the well-known sites, you eventually have a pretty good idea of what to expect. But what secrets does the Haringvliet hold, for instance? And what are the ecological consequences of the Kierbesluit — the partial opening of the Haringvliet sluice — for underwater life? Before the Delta Works, eels, trout and herring moved freely through the brackish water here. What does it look like now? And where will I find the fish hotel that was installed five years ago? Questions like these make a dive exciting and unpredictable.
Another absolute favourite is Slot Hulkenstein in the Randmeren. You dive no deeper than three or four metres, gliding alongside old foundations, stacks of historic stonework and structures where you can make out a courtyard or a kitchen. As you hover there, you mentally trace the outlines of the castle and history from hundreds of years ago suddenly comes to life. Those are the dives I mark with a gold star in my logbook."

You have spent countless hours diving in your home country. What is the most extraordinary encounter you have personally had — a moment when you truly felt at one with nature?

"Without a doubt, it was the moment I came face to face with a colossal pike beneath the restaurant at the Haarlemmermeerse Bos. Enormous, majestic. It hung there motionless in the water, completely indifferent to my presence. For several minutes we stared at each other in breathless silence, until it eventually decided, very calmly, to move on. That intense feeling of mutual respect is something I will never forget."

Every spring, your calendar revolves around the mating ritual of cuttlefish. What is it like to witness such an intimate and fragile natural wonder in our own Zeeland waters?

"The cuttlefish is an almost un-Dutch, exotic creature, yet it has become an inseparable part of Zeeland. When the timing is right, you find several large cuttlefish at the specially placed spawning poles, their arms entwined as they mate. The female then swims to a spot she has approved and carefully attaches her eggs to a pole or a tube worm. Meanwhile, the male hovers watchfully above her to protect her, making sure no rival male moves in to deposit his own sperm packet. This sometimes leads to a fierce underwater battle, though often it amounts to nothing more than an imposing display of presence. It is beautiful to watch him place an arm over the female in what looks almost like a tender, protective gesture. When you can hang there motionless as a diver and witness all of this at such close range, you feel a profound admiration for our own natural world."

You align your diving schedule entirely with the natural cycle of the seasons. Does that make you feel more connected to the rhythm of the earth above water as well?

"Absolutely. As a nature guide for IVN, I work with the natural cycle every day. The stories I tell children are always tailored to what has just happened, what is blooming right now, and what the logical next step will be. I want to give them a sense that nature is not a static snapshot but a dynamic process that is fundamentally part of our own existence. Underwater, it works in exactly the same way. If you dive often enough, you start to recognise patterns. You know precisely when certain species appear, mate, migrate or make way for others.
To be honest, the number of dives does drop off a little in the winter months. I limit myself to the absolute highlights — such as the arrival of the first sea slugs, which sometimes appear as early as January or February to lay their eggs. But I also love the young Tubularia. For me, just like the first tulips above water, they herald the early spring."

With DiveActivity you also organise expeditions to shipwrecks on the open North Sea. The transition from a calm shore dive to the vast, rugged North Sea is enormous. What does your personal connection with nature seek out on those deep wrecks?

"Wrecks carry a tangible history with them. I find it both fascinating and humbling to immerse myself beforehand in the story and the sinking of, say, the three cruisers lying in the North Sea. During the descent, that history suddenly takes on a very physical dimension — for a brief moment, you experience that era yourself.

At the same time, the biological aspect is breathtaking. It is extraordinary to see how a wreck transforms into a living artificial reef. Although life in the North Sea is under enormous pressure in many places due to human activity, an abandoned ship's hull becomes a true paradise for mullet, cod, turbot, tompot blennies and enormous North Sea crabs. It is a wonderful combination: you are literally diving into history while watching nature reclaim a structure that humans left behind."

For someone who has never dived in the Netherlands: what is your personal top five of dive sites?

"That is always an incredibly difficult question. What is an absolute top spot today can easily disappoint tomorrow. Factors such as tidal currents, visibility, the season and simply a measure of luck all play a major role. But if I have to take a shot at my favourites, I would choose these five gems:

•    Plompe Toren (Zeeland): A stunning underwater landscape with frequently rich biodiversity.
•    Zeelandbrug (Zeeland): The go-to hotspot for cuttlefish in spring and an iconic dive.
•    Vlietepolder Pijlhuisje (Zeeland): A dive site with a very distinctive, intimate character.
•    Spiegelpolder (Spiegelplas): Known for its often exceptional visibility and beautiful freshwater flora.
•    Haarlemmermeerse Bos: The place where I had that majestic encounter with the giant pike."

On 6 and 7 February you will be sharing your passion at Duikvaker 2027. What do you hope your personal story will spark in the divers in the audience who are still on the fence about diving in the Netherlands?

"Above all, I hope it flips a switch and gives them the courage to go and explore for themselves. Don't always automatically follow the dive club to the same safe, familiar site — just try something completely different for once. There are hundreds of dive sites across the Netherlands waiting to be discovered. Yet I am almost certain that most divers end up with a list of around ten regular spots they keep returning to.
Dare to break that routine. Pull out a map and pick an unknown site. Yes, maybe the visibility will let you down once, but there is just as good a chance that you will discover something you never expected. You will be amazed at what you encounter in those unexplored places. For me, it is precisely that unknown element that is the most important and most beautiful part of the adventure of diving in the Netherlands."

Want to hear more about the hidden gems of Dutch waters, spectacular wreck dives or photographing cuttlefish? Come to Duikvaker on the weekend of 6 and 7 February 2027 and let yourself be inspired by the stories and expertise of Rob Dekker!