It looks like there are yeah.
Here at least no one worries about the water supply, it should be ok.
You have those reservoirs fenced off? Here they are free to stroll around yes. You can even go fishing but only with a bot with no engine. I wouldnt go swimming in there. The water does not look that appealing even though its clean.
If I want to swim then we have a ton of coastline with beaches. Or go to lakes or quarry lakes with pristine blue water. So yeah, there's no demand to swim on this reservoir 😄
Photos might make you feel that way. In reality it was damp and dull weather with +6 or so degrees C.
The most important ones are fenced off or built in a way that you can't access them, e.g between cliffs. Also, fishing is forbidden. I think that they are also fenced off for safety as some reservoirs are built in place of former villages which were not fully destroyed, and also there are plenty of old trunks close to the shore.
Yes, yes, you are lucky to have the coastline in Estonia 🙂