What do you call the green slippery thing formed, due to standing in water?

I want to know the term in English for the green slippery substance formed on things that are standing in water. I can only think of "algae" or preferably "green algae"; these are in the context of science.

But is there any other general word in English used for this green slippery thing? In Hindi we say, Kaayi, so what is Kaayi in English?

Solution 1:

A generic word is slime: Slime algae on backyard ponds. This could occur on the surface or on the side of tanks.

slime noun

2. a. A viscous substance or fluid of animal or vegetable origin
(in this sense: 13th century)

[OED]

Solution 2:

The closest English word I can think of is "scum" (but "pond scum" completely matches your definition);

scum n. a layer of dirt or froth on the surface of a liquid.

pond scum n. Any of various freshwater algae that form a usually greenish film on the surface of stagnant water.

Solution 3:

Here in Madison, Wisconsin, we use the scientific term, Algae. People call it Lake Algae because Madison is situated on 4 lakes and that is where it forms and is often observed.

Lake Algae article