sub-aqueous en · ADJ
Etymology
From sub- + aqueous.
Meanings
-
(alt-of, alternative, not-comparable) Alternative form of subaqueous.
alt of subaqueous
[...] he'd been hoping to build a bridge over the River Nova in St Petersburg. The Russians would eventually decide to go under the river, but not before Brunel had shown the way, by building the first sub-aqueous tunnel in the world.
2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, →ISBN, page 87:The tunnel is 4 miles 628 yd. long, and is the longest tunnel on a British main-line railway, and the longest sub-aqueous tunnel in the world.
1948 September and October, “Weekend Works in the Severn Tunnel”, in Railway Magazine, page 298: