Can the body of water be under control by different members of a close-knit alliance, like the EU?
Hiroshima not taking Little Boy but rather dozens of carpet bombings would be better ?This seems too generic to never have been done, but
A Softer World
A map of a region whose history was better (less violent, more prosperous, more democratic, etc) than in OTL
(this wouldn't necessary mean utopia, just better)