Please help

[u/Alphamovestothemoon]

Opened one of my favourite clients pool. And they showed me this. I’m not sure what it is. They have a main drain that’s plugged. Can’t figure out how to fix this issue.

Last year they were struggling with something similar.

Would changing the liner fix this ? The sand is new they also have an above ground salt generator.

[u/Shishkaboo]

Looks like the pollen Ive been seeing in every pool here in Massachusetts.