Google says 'viperine snake (Natrix maura), also known as the viperine water snake. It is a non-venomous snake that is often mistaken for an adder due to its similar appearance'.
If it turns out, that Google is wrong, don't blame me
Toni posted a little video of it on Facebook for anyone who would like to see it: Puerto Pollensa Snake Video
It was really cool to see, but whether it's venomous or not, I'm going to have to inspect every inch of the pool before I get in now and sunbathing is going to be 100% less relaxing!
Google says 'viperine snake (Natrix maura), also known as the viperine water snake. It is a non-venomous snake that is often mistaken for an adder due to its similar appearance'.
If it turns out, that Google is wrong, don't blame me
I did some research too and I think you're right. We helped it out of the pool, but weren't fast enough to catch it. So it slid off into the stone wall. We've not seen it since