The term 'OLD POOL DENIZEN' can be solved by the crossword solution 'STENO', which is a five-letter word. Steno is short for stenographer, which is a person who specializes in taking dictation and transcribing it into written form. This job was especially popular in the past, when typewriters and computers were not yet available. Therefore, an 'OLD POOL DENIZEN' could refer to a stenographer who has been in the profession for a long time.