The Collaborative International Dictionary of English v.0.48:

Submersed \Sub*mersed"\, a. [L. submersus, p. p. of submergere.
   See Submerge.]
   Being or growing under water, as the leaves of aquatic
   plants.
   [1913 Webster]

WordNet (r) 3.0 (2006):

submersed
    adj 1: beneath the surface of the water; "submerged rocks" [syn:
           submerged, submersed, underwater]
    2: growing or remaining under water; "viewing subaqueous fauna
       from a glass-bottomed boat"; "submerged leaves" [syn:
       subaqueous, subaquatic, submerged, submersed,
       underwater]