From The Collaborative International Dictionary of English v.0.48 [gcide]:
Submerge \Sub*merge"\, v. t. [imp. & p. p. Submerged; p. pr. &
vb. n. Submerging.] [L. submergere, submersum; sub under +
mergere to plunge: cf. F. submerger. See Merge.]
1. To put under water; to plunge.
[1913 Webster]
2. To cover or overflow with water; to inundate; to flood; to
drown.
[1913 Webster]
I would thou didst,
So half my Egypt were submerged. --Shak.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
submerged
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]