OK. The pump strainer basket, and the main drain cover. Don't think I'd offer to swim down to get that, either.

Dead algae is brown, so that's probably a good thing. Continuing to keep the chlorine high is the right thing to do, especially if you have piles of algae. Otherwise, the pile will consume the chlorine when you brush up the algae, and leave you with a pool no chlorine and lots of live algae -- NOT a good thing.

Just FYI: when you have layers of algae like you describe, the total consumption of chlorine, before you finish, can be enormous. So, don't be surprised.