It is prohibited to take Marimo green ball made of water weeds. Even if the water weed is not in the shape of ball, you must not take the weed from the lake.
Because the Lake is under the reign of deities called Kamui different from that of the main island of Japan.
Please take enough time to savor the scenery and the culinary delights sourced locally in the eastern part of Hokkaido. The atmosphere is so mysterious that even I have never dive into the lake before.