I recently heard about this crazy Year 1910 plan to bring hippos into the Louisiana Bayous for Water Hyacinth control and meat production . Never got off the ground but Cajun life would certainly be different today if it had . Here is a link to an article in Wired about it :
Not sure if hippo are the right model - they can be pretty mean beasts. I do NOT want one for Christmas. Steller's Sea Cow could be an option - except they're extinct.