I don’t understand why fish has to be so efficient? Why not just make it as a bonus income for people who want an eco boost without going 2TC. Then it wouldn’t feel so bad to lose water. And water can be used in other strategic ways design-wise, like controlling certain parts of the map.
I’d say winning water and having an income that’s impossible to contest or raid is a good enough reason to go water, without the need of making it mandatory via an artificially high gathering boost.