What is a collective noun for float?

There isn't a commonly used collective noun specifically for "floats" in the sense of decorated vehicles in a parade.

However, you could use some general terms depending on the context:

* A procession of floats

* A parade of floats

* A display of floats

* A fleet of floats (if it's a group of boats decorated for a special occasion)

You could also be more specific about the type of floats:

* A line of carnival floats

* A collection of holiday floats

* A squadron of parade floats (using a military term for a group of aircraft)

Ultimately, the best collective noun depends on the context and the specific type of floats you are referring to.