Aachtopf (Aachquelle)
Germany's largest karst spring, at the town of Aach in the Hegau, fed largely by Danube water that seeps away upstream. Divers have followed the mostly water-filled passage about 400 m in a straight line from the spring pool, with only a short dry stretch in the 'Seenhalle', until a collapse blocks the way after about 600 m. Strong flow and murky water make it one of the hardest cave dives in the country, and it has only been roughly surveyed. In 2015 a cave diver discovered pale loaches here – the first cave fish known from Europe.
Tiefe: 0–18 m