Fwiw, I think it makes great snail food. Mystery snails seem to like brassicas & watercress is a brassica plus it is possibly the most nutritious of the lot.
One nutrient mystery snails need in minute amounts is iodine but it’s not available from many sources & those sources are all marine.
Mystery snails & their relatives would probably eat seaweeds but if you give them cooked or blanched cress, they’ll get the iodine they need along with a fair bit of calcium & a long list of other nutrients. I only recently learned that cress is one of or maybe the only terrestrial plant that offers any iodine.
I wish I liked cress myself but I don’t. But it’ll grow submerged and even float for awhile, though eventually it gets topheavy and rolls over, which is not attractive🙂.
It could be one way to provide free food for snails if you keep them.
