Submerge, v. t. [imp. & p. p. Submerged; p. pr. & vb. n. Submerging.]
Etymology: [L. submergere, submersum; sub under + mergere to plunge: cf. F. submerger. See Merge.]
1. To put under water; to plunge.
2. To cover or overflow with water; to inundate; to flood; to drown. I would thou didst, So half my Egypt were submerged. Shak.
1 other Webster entry under this spelling
Submerge, v. i.
To plunge into water or other fluid; to be buried or covered, as by a fluid; to be merged; hence, to be completely included. Some say swallows submerge in ponds. Gent. Mag.
Shades of meaning
Fernald has no entry of its own for submerge; he lists it under immerse.
Where he writes about it:
To dip and to immerse alike signify to bury or submerge some object in a liquid; but dip implies that the object dipped is at once removed from the liquid, while immerse is wholly silent as to the removal. — from immerse
Submerge implies that the object can not readily be removed, if at all; as, a submerged wreck. — from immerse