Cleaning iPhone speakers from dust by putting the iphone in water

I'd never advise anyone to intentionally immerse an iPhone, even with its purported waterproof rating.

Pretty sure even if you did it wouldn't clear dust from the speakers due to surface tension.

A gentle blow and a soft brush is likely your best path.

An iPhone is not waterproof. Do not ever put it in water. If you do put it in water, you will destroy it.

There is no version of iPhone that is waterproof. Submerging is not a good idea.