What Are These Insects?

I keep my bath clean. I have checked under the bath, and have put bleach down the drains, but every morning when I switch the light on, there are some creatures in there. They are about half an inch long, have a rounded head and a pointed tail, similar to this c>. They are usually dark coloured. They don't appear to have eyes or legs, but wriggle about a lot. Where are they coming from and what attracts them to my bath?