{n. phr.} One of many; not the only one of the kind; not the only one available. * /He said he could find other girls - she was not the only fish in the sea./ Compare: NOT THE ONLY PEBBLE ON THE BEACH.
NOT THE ONLY FISH IN THE SEA
Meaning of NOT THE ONLY FISH IN THE SEA in English
Slang English vocab. Английский сленговый словарь. 2012