that your pic? lemme know what happens, i assume the plant will drown. the stomata getting clogged i think would be a issue and if it lived flower would be impossible.
Aquaponics, google it. One of the members here filled a hot tub with fish and grew plants in floating styrofoam sheets.
Do you put it in the aquarium while it's little or after it grew? Is it able to grow when surrounded by water? Do the fish help somehow with it? This might be perfect to not get detected because of the smell. I have a 300L aquarium, I might fit a few plants inside. Recently I found some worms inside, which might have come with a few live rocks that I got. Or the coral, who knows. Maybe the next time they'll decide to smoke some and just chill, not hunt my fish. I had to lose a few fish until I detected them. Just take a look on http://arcreef.com how ugly and disguisting they are.
You can't put whole plant underwater.. Not if you want it alive anyway xD aquaponics/DWC may be the option with a fish tank, not sure how well nutrients would work with fish.. But in theory you wouldn't need to do water changes, only top up your tank. my best idea is to make a stealth cab underneath, at least you won't have to worry about the noise.. Just my 2c anyway