Sea Slug and the Turtle: Den Osse Nieuwe Kerkweg, Scharendijke

Netherlands dive #3

Entry: 9:51am

Dive time: 51min

Depth: 24.7m

Temp: 10 degrees C

Weights: 11kg (NO ankle weights)

Insulation: Dry suit

Den Osse is a hamlet in Zeeland on Lake Grevelingen with Nieuwe Kerkweg translating to 'new church road'. Lake Grevelingen is the largest saltwater lake in Western Europe. The lake was created through the construction of a dam, the Brouwersdam.

Fred

In 1953 there was a devastating North Sea flood, considered the worst in Dutch history, which resulted in the sad loss of 1,836 lives, 30,000 dead livestock, 340,000 acres flooded and 47,300 damaged buildings.

Stellendam after the devastation left by a flood on the island of Goeree-Overflakkee in the Netherlands.

The Dutch struggle against water has long been woven into their history and has been associated with the formation of their economic and social policymaking known as the poldermodel, a method of consensus decision-making. On first sight, a polder appears to be just a field. However, it is actually a low-lying tract of land that has been reclaimed and enclosed by embankments known as dikes. Three types of polder exist; those reclaimed from a lake or the seabed; flood plains separated from the sea or river by dike; and marshes separated from the surrounding water by a dike and subsequently drained. It was in the interest of all living near rivers, the sea and delta swamps to collaborate in the prevention of flooding and the reclamation of land. This led to intense negotiation practice between government, non-government and private parties to make up the polder area. As noted by FAO: "The physical and institutional polder culture is indeed a crucial aspect of the Dutch national identity".

The flood of 1953 was the last of its kind in the Netherlands. The problem of flooding however causes unprecedented devastation all over the world and as I type, overflowing rivers has so far led to 107 recorded deaths in Brazil and many more missing people. The Dutch government embarked on one of the most elaborate engineering projects in history, the Delta Works. This involved the construction of the Browersdam which isolated Lake Grevelingen from the sea and seawater entering the lake is now entirely controlled by the Brouwers sluice gate. Zeeland (Sea Land) is in fact the most watery part of the south and is where the Delta Works were constructed.

Shutting off the sea connection resulted in a dramatic change in the ecology of the area. Salt meadows have now become overgrown with tough herbs, grasses and trees, while the lake is home to numerous migratory bird species which spend the winter in the Netherlands.

I'm a big fan of TED videos and use them regularly in my lessons to engage learners. Watch this one to find out more about the Delta Works and why many locals believe that "God created the world but the Dutch created the Netherlands".

This dive site is really popular. My colleague Fred and I were first to arrive having departed The Hague at 7:30am and arriving just over an hour later. There was a large diving group from Germany. One also frequently hears the voices of Belgian divers as well with Antwerp under 90 minutes away by car.

The dike encircling the Grevelingen Lake is composed of stepped banks which you have to climb with your tank and weights - it can be a little tiring! The dikes are called 'muralt walls' named after R.R.L de Muralt, an engineer who worked for the Schouwen Water Authority. These walls were built in response to an earlier storm surge in 1906. Since then until 1953 approximately 120 kilometres of sea dike were constructed in Zeeland with this structure.

The area is ecologically rich and diverse with the seabed teaming with aquatic life. On my first dive here I saw loads of nudibranchs, my favourite! On entry in the water the bottom gently slopes down to a sandy floor. After twenty meters or so there is a small underwater stone dike which upon passing leads to deeper water. Our maximum depth was 24.7m.

LOTS of Sea goosberries also known as Comb jellies (Pleurobrachia pileus). In Dutch they are called Zeedruif which translate to Sea grape. You can often miss them as they are so small (the body around 2cm while the tentacles can be up to 15cm long) and float past your peripheral vision but they are absolutely amazing to look at! The iridescence is really quite hypnotizing. This phenomenon makes the surface appear to change colour similar to that seen in a soap bubble. Wave interference of light in the microstructures or thin film cause the effect. They are often mistaken for jellyfish drifting through the surface waters.

They can swim, as seen in the videos below, by beating their comb-like plates of fine cilia. They make little headway against the current and so often gracefully float along with the current.

Zeedruif met razendsnel trillende ribplaatjes, by Nudibranch Marine Discovery Productions (Peter van Rodijnen); Stichting Natuurbeelden, is licensed under Creative Commons – Attribution-Share Alike.

Common prawn (Palaemon serratus)

Identified by its pinkish brown colour and reddish stripes.

It can also be seen in waters around the UK.

Common crab (Carcinus maenas)

Common goby (Pomatoschistus microps)

Gobies form part of the Spiny-rayed fish, the largest andmost recently evolved group of fish. Spiny-rayed fish account for about half of all species. Given this great variety, there is a wide range of colours, shapes, behaviour and specialized adaptations. The gobies are some of the smallest types.