About 50 miles outside of Hamburg in northern Germany is an old opencast chalk mine, which was later flooded by groundwater seeping up from below as the mine reached deeper and deeper. Eventually, the entire mine filled with fresh water when mining stopped in the 1970s. The factory buildings surrounding the mine were torn down, and some of them were dumped into the lake to support the edges.
In the 2000s, Hemmoor Kreidesee (Kreidesee means “chalk-lake” in German, referring to the mining origins of the lake) became a popular dive destination. A number of artificial reefs were placed in the lake to support the diving and a dive center has sprung up near the entrance to the lake area.
The draw of the lake is not the temperature of the water, which hovers around 57 or 58 degrees Fahrenheit (14 C) year-round, but rather the visibility, which can be as much as 100 feet. The bottom is somewhat silty, however, so on popular days with lots of dive courses going on, viz can quickly drop to only a few feet in popular areas. Luckily, the lake is huge and it’s usually possible to find a different, undisturbed location.
The real draws here are the old structures that pre-date the flooding. When you enter the lake, you follow the old access road into the mine, swimming along the dirt road, which features a railing towards the mine side. Several buildings and a flooded forest still stand in the depths as you descend into the lake. The wrecks of cars and small boats have been placed in the lake over the years, adding further appeal and mystery to the site. The lake is also home to lots of crayfish and trout, and the latter in particular tend to be quite curious.
If you like deep diving, Hemmoor is also a great destination. With a maximum depth of 200 feet (61 m), but no discernable current, the lake lends itself very well to technical diving or technical diving training. Of course, only properly certified divers or those in training should attempt depths beyond recreational diving limits. But for recreational divers, the depth allows for a feeling of bluewater diving, where all you can see around is water — no surface, no bottom, no reef, no wreck. Keep your eye on your depth gauge for this experience, as it is easy to drift up or down in the water column when you find yourself without a depth reference.
Because of the lake’s depth and temperature, a drysuit is highly recommended. Also, local regulations require all divers to dive with an independent backup regulator. An octopus is attached the same first stage as the main regulator, making it dependent on the same first stage and valve, so anyone planning to dive Hemmoor Kreidesee must obtain an independent regulator, which has its own first stage and its own valve. This can be achieved by using a single tank with a double valve, a pony bottle, or by using a tech diver’s setup with twin tanks.
