I can't say whether the work reported is defensible, but I can say that (1) chloroquine is not available over the counter in the US as it is in many places, (2) it can be dangerous, even fatal if misused, and (3) it is available in the US in pet stores for treating aquariums.
So, provided you only put it in the tank you swim in, you should be OK, but I don't know about the safety of chloroquine phosphate taken orally. Still, if you are on the down slide, it might be preferable to risk it, and also to have some on hand against such an event.
Hydroxychloroquinine is the drug that my father received during World WarII to treat Malaria tropica. The high dose worked so well on him, that he never again had a malaria attack. But unfortunately he developed severe liver damage as a consequence of the high dose, from which he never completely recovered.
So, provided you only put it in the tank you swim in, you should be OK, but I don't know about the safety of chloroquine phosphate taken orally. Still, if you are on the down slide, it might be preferable to risk it, and also to have some on hand against such an event.