So as our overseas friends get the picture, the River Tees was one of those rivers in the North East of England ( which is definitely NOT noted for warm weather ) which, by the 1950's was heavily polluted from at least 100 years of uncontrolled steel and chemicals ndustrial usage .
Vin Garbutt wrote a song " the Valley of Tees " .
Harking back to when it must once have been a clean normal river with salmon he began " Pink dorsal fins swam in the clear crystal Tees ........"

A good mate of his and mine, Plonk Inlgedew learned the song and on his first public rendition began " Pink dolphins once swam in the clear crystal Tees ........"

Wow - we p8ssed ourselves laughing , but the unwitting Plonk needed to have it explained to him - and blamed Vins poor diction in the rendering of the song on his first LP.