It happened to me too! I was carefully watching next to my bee nest I managed to create after growing an oak sapling next 2 blocks to a flower, when I saw a bee dive straight into a one block deep river, but the bee didn't get out of there at all, it kept drowning inside the water, not only that but all the other bees I had also disappeared, and I'm not 100% sure they died, maybe they all as you said touched the water and forgot about their homes
This is a typical behavior with ghasts too, they dive deep in lava & water, but water is the only danger for them as they stay in it long enough to drown.
It happened to me too! I was carefully watching next to my bee nest I managed to create after growing an oak sapling next 2 blocks to a flower, when I saw a bee dive straight into a one block deep river, but the bee didn't get out of there at all, it kept drowning inside the water, not only that but all the other bees I had also disappeared, and I'm not 100% sure they died, maybe they all as you said touched the water and forgot about their homes
This is a typical behavior with ghasts too, they dive deep in lava & water, but water is the only danger for them as they stay in it long enough to drown.