Source : Webster's Revised Unabridged Dictionary (1913)

Water mint \Wa"ter mint`\
   A kind of mint ({Mentha aquatica}) growing in wet places, and
   sometimes having a perfume resembling bergamot.

Source : WordNet®

Mentha aquatica
     n : a European mint that thrives in wet places; has a perfume
         like that of the bergamot orange; naturalized in eastern
         North America [syn: {water-mint}, {water mint}]