subaqueous

Once, indeed, the raft grounded upon a subaqueous reef, and threatened going to pieces.

The shadow of the house had swung over it, and in the gathering dusk the flower-beds glowed with a dim subaqueous radiance.

The Loudoun formation, of course, followed a period of erosion of the Catoctin Belt, since it is the first subaqueous deposit.

The difficulties in making a subterranean or subaqueous railway are only too clear.