The correct meaning of "hoist" and "float" [closed]

There is an excerpt from the book Shoe Dog by Phil Knight:

Woodell and his twenty frat brothers were hoisting a float down to the Millrace, a stream that wound through campus. They were trying to flip it over and someone lost their footing. The float collapsed.

I want to know what is the meaning of "hoisting a float down to the millrace". I've looked up on Google where millrace is a stream of water but what is the meaning of "hoisting a float down" and "the float collapsed"? I am not a native speaker of English so it would be very thankful to clear the right context of these words.

"Float" can be one of several things but Merriam Webster gives definition 2.b. as

a floating platform anchored near a shoreline for use by swimmers or boats

which is the most likely definition in this case.

The same dictionary gives this definition 1 of 'hoist' as a verb

: LIFT, RAISE especially : to raise into position by or as if by means of tackle

("Tackle" in this case being some kind of lifting equipment)

So the whole phrase "hoisting a float down to the Millrace" means lifting a floating platform off the bank using some sort of lifting equipment and lowering it down into the watercourse called "The Millrace".

"They were trying to flip the float and the float collapsed" means that, as they were trying to turn the float over, it either folded up or broke. Perhaps it wasn't a very well-made float.

You could probably have found these definitions yourself but the words "float" and "hoist" have so many different meanings that I can understand why you would have difficulty working out which one was being used in this case.

As a further complication this use of "float" is not really a British English one, it only seems to appear in Merriam Webster which is an American dictionary.