Right, Most could have simply walked out on ther own. Even non swimmers...provided they didnt step in a deep hole. A stick to probe with could have helped avoid those. Its not like there was much of a current to sweep anyone off their feet.
An open wound and infection from the dirty water would be the biggest risk. Probably 10 of thousands could have simply walked the hell out of NO.
Ferrying people in a boat through calm shallow water really isnt a rescue imo. Most of those were probably no swimmers who let their fear of drowning over rule their common sense.