That looks like Dracaena. Very common and indestructible houseplant.
I don't believe it's aquatic, nor even semi-aquatic. My best advice is to remove it and pot it up in a sunny window, and hope for the best.
Well crap! It was completely submerged in one of the tanks sold as aquatic plant. I told her I was putting it in a goldfish tank. But they did have bamboo offered as an aquatic plant and I wasn't sure if it could be completely submerged in the tank. So that stinks!
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