Webster's 1828 Dictionary
SUBAQUATIC, SUBAQUEOUS
a.[L., water. ] Being under water, or beneath the surface of water.
Webster's 1913 Dictionary
SUBAQUATIC; SUBAQUEOUS
SUBAQUATIC; SUBAQUEOUS Sub `a *quat "ic, Sub *a "que *ous, a.
1. Being under water, or beneath the surface of water; adapted for use under water; submarine; as, a subaqueous helmet.
2. (Geol.)
Defn: Formed in or under water; as, subaqueous deposits.
New American Oxford Dictionary
subaquatic
sub a quat ic |ˌsəbəˈkwätik, -ˈkwa- ˌsəbəˈkwɑdɪk | ▶adjective underwater: a narrow, subaquatic microclimate.
The Wordsmith Dictionary