It needs constant water. You could grow it in a container though. Not one with a drainage hole
Information here http://www.theguardian.com/lifeandstyle/2013/jan/26/gardening-alys-fowler-grow-watercress
If watercress isn't feasible, try American Land Cress. Tastes very like watercress but grows in soil like any sensible vegetable would.
I grew watercress a few years ago in my greenhouse, I just used some wide plant pots in a tray of water, they did quite well.
I grow it in "self watering" troughs, which hold water in the base. I keep it in semi shade, water well each day & tip troughs to get rid of old water every few days and then re-water. At times more compost needs adding.
thanks! Might try the American land cress as the other sounds a bit fiddly.
Watercress is easy. A bunch from the shop and your away. It reaches weed status in my pond at times