Picture your favorite hiking trail.

Now imagine going for a swim through this same patch of land—seems weird and perhaps impossible unless an apocalyptic flood occurs.

In Styria, Austria, there is a park that only exists during part of the year.

“But I thought this was a park…” Has likely been said before, if one tries to return to visit the county park at Gruner See in the summer time.

During the summer the park turns into a full-size lake up to 12 meters (nearly 40 feet) deep.

Towering above the lake/park are rows of mountains, known as the Hochschwabb Mountains.

During the winter these mountains are packed with glistening snow, but when the heat of spring kicks in, all of the snow starts to melt. As it runs down the sides of the surrounding hills it falls directly into the park. Looking up at the hills you can actually see where the water has left behind a path that flows directly down into the summer lake.

In the winter a small lake is present, but remains isolated to a small area of the park. The water is also much more shallow, at no more than 2 meters (6.5 feet) deep. As the water rains down from the melting peaks, the lake spreads far and wide, reaching up to 40 feet deep in places.

It seems rather perfect, a lake that forms just in time for summer.

But before you start thinking about which swimsuit to wear, you don’t want to go swimming here without proper protection. The waters retain their icy qualities and at warmest reach only 40 degrees.

If you have diving gear there are some incredibly unique sights beneath these waters. After all, it’s not an abandoned park; in a few months the hikers will be back to enjoy the trails and all of the other amenities currently underwater.

There are benches, a bridge, and plenty of vegetation, as if no water has flooded the area. The water doesn’t seem to get in the way too much, all of the squirrels have hopefully run off, but the vegetation still blooms beautifully.

Divers enjoy seeing the underwater park, swimming down clearly marked trails and sitting on a bench in the middle of a grass field. Looking up from the waters surface also offers a nice view, the tall mountains and green peaked trees on all sides of you, blue skies and white clouds up above.

Plus, you can see everything under the water because it is incredibly clear.

When snow melts it produces the clearest water, leaving many to question why the water in the lake appears green. This has to do with all of the grass and vegetation that grows at the bottom of the lake. This is a park and hiking trail FULL of vegetation, and so when you fill it up with lots of water, all of the greenery reflects onto the surface and casts a green glow.

This underwater park also includes fish, not many but you do see some here and there. They come from the smaller lake always on site, meaning they enjoy a way bigger house in the summertime.

Just before the water starts to rise and flow, I wonder if they get excited, and when the lake starts to recede in July, are the fish disappointed to down size?

The world may never know. But by winter the divers disappear, the fish return to their smaller lake, and the hikers enjoy some much-missed scenic exercise.