Yes of course but recording a private conversation has been legal before and I couldn’t find any good indications that it has changed under the GDPR.
The law essentially says that it’s illegal to record or listen to private conversations which you aren’t a part of using technical instruments.
So it’s legal to press your ear against a wall but it’s illegal to use any tech to listen/record to anything.
It starts fairly close to the sea but takes an enormous detour to get there.
(Yeah I know that the geography probably doesn’t allow the river to go anywhere else. It’s a joke.)