pelagic
/peˈlædʒɪk/adjective
1- technical of or relating to the open sea〈技〉（与）远洋（有关）的：
the kittiwakes return from their pelagic winter wanderings.
三趾鸥从冬季远洋漫游中归来了。
1.1
- (chiefly of fish) inhabiting the upper layers of the open sea（主要指鱼）栖居上层水面的, 浮游的。常与DEMERSAL相对。
词源
mid 17th cent.: via Latin from Greek pelagikos, from pelagios 'of the sea'（from pelagos 'level surface of the sea'）.