Our family has a good-sized pond with fish in it (for fishing) and sometimes people like to paddle-boat, kayak or canoe. Plus we have picnics there, etc.
This algae you mentioned, can it be grown in a fishing pond? Will the two work together? The algae wouldn't kill the fish, or the fish wouldn't eat all the algae, would they?
Occasionally my cousins swim in the pond but I don't, yuck! They end up with some "fish hickeys", anyway. But I might go swimming there if this beneficial algae was growing on the water.