Kreidesee Hemmoor

Chalk was quarried at Hemmoor from 1862, first for lime and brick, then from 1882 under the Portland Cementfabrik Hemmoor, whose cement was shipped worldwide. Output passed a million barrels a year by 1910. The pit reached almost 120 metres deep in its oldest section, worked with a bucket-wheel excavator whose terraces are still visible underwater today. Extraction stopped in 1976: separating flint from the chalk had grown too costly, and the rising groundwater threatened a nearby federal road.

The pumps were switched off and the pit slowly filled with spring, ground and rainwater, becoming a lake by around 1982; parts of the backfilled western bank slid as the water rose, leaving the unusually flat lake bed seen there today. The works were demolished from 1985, and sport divers, led by Holger Schmoldt and Ulf König, had already found the flooded pit the year before and begun mapping it. Word spread through diving magazines and word of mouth, and visitors scrambled down bare, rope-secured slopes to reach water with no diving infrastructure at all. Schmoldt turned professional in 1996, building the dive base and campsite and agreeing rules with the local authority.

Diving today runs from six numbered shore entries, E0 to E5, each a pontoon or platform reached on foot or by car. E0, E1 and the two halves of E4 are the shallow, beginner-friendly ends of the lake; E2 and E5 mix flat ground with sections that fall away steeply; E3, open only to divers with 40 logged dives including five in cold water, is closed to training altogether. Scattered around them are the sunk and left-behind attractions the lake is known for: a hovering light aircraft, cars, a caravan, a yacht and the ruined vibrating-screen plant and access road of the old works, plus a near-vertical wall and stands of drowned trees on the slope beneath it.