Lake Bohinj is a flow-trough lake. At the western end, cold water from the Savica waterfall flows into it, while at the eastern edge it drains into the Sava Bohinjka.
The lake basin contains 92.5 million cubic metres of water. The water stays in the lake for about four months before it drains out of the lake. According to this estimate, all the water in the lake changes three times a year. In the middle of the Bay of Fužina on the eastern side, Lake Bohinj reaches its maximum depth of 45 metres... more than the depth of the Slovenian sea. The shore is about 11 kilometres long.
Lake Bohinj is known as a cold lake, but it can warm up to 26°C at the surface in summer, and its surface has frozen in winter until recently.
Lake Bohinj offers plenty of leisure activities. In the warmer months, you can swim, boat, kayak, canoe, surf or go with a sup. For vessels (including SUP), you need to purchase a permit in advance. You can also fish or dive, though a permit is required for these activities as well. You can take a tourist boat, walk along the lake shore, but cycling is only allowed on the road along the southern shore of the lake.