crud ring 

The collection of organic or inorganic residue that collects at the water line of hot tubs, bath tubs, sitz bath or any other standing water, after it has been violated by people who refuse to shower before entering.
The residue may be a combination of sweat, hair, various body fluids, chemicals, beauty products, herpes simplex, excrement and other undisolved as yet unclassified solids and other things to numerous to mention. It may be easier to define it in the aggregate as "Nasty shit you don't want to touch"

I am not getting near that crud ring!

crud ring by Juan Moore Beer April 10, 2017

crud ring 

The collection of organic or inorganic residue that collects at the water line of hot tubs, bath tubs, sitz bath or any other standing water, after it has been violated by people who refuse to shower before entering.
The residue may be a combination of sweat, hair, various body fluids, chemicals, beauty products, herpes simplex, excrement and other undisolved as yet unclassified solids and other things to numerous to mention. It may be easier to define it in the aggregate as "Nasty shit you don't want to touch"

I am not getting near that crud ring!

crud ring by Juan Moore Beer April 10, 2017