“+ adjective
Etymology: sub- + aqueous
1.
a. : being or found under water or beneath the surface of water
viewing the subaqueous fauna from a glass-bottomed boat
b. : adapted for use under water : submarine
a subaqueous helmet
c. : suggesting or typical of the underwater world (as in remoteness or dimness)
a soft subaqueous light
the subaqueous world of the underconscious — Vernon Young
2. : formed or taking place in or under water
subaqueous canyons