I hope the picture is clear enough, I've found a worm like insect like the one below a little while ago in my shower, and today I found another one. I've never seen something like this. I would say it is slightly bigger than a centimeter.
Silvefish are well known very resistant pest typically found in washrooms and sometimes in kitchens. They are not directly dangerous but can cause property damage. Here is a webpage giving advice on how to get rid of them