Cetacean Ops was a facility on board the USS Enterprise-D, in an alternate universe created by a time traveling USS Enterprise-C. (TNG: "Yesterday's Enterprise")
The term "Cetacean Ops" was only heard in the "background chatter" during the episode. The existence of a comparable facility was canonized in the episode "The Perfect Mate", but it was not mentioned by name in that episode. To date, the facility has never been shown on screen. Conceptual artwork at Andrew Probert's website shows that the facility may be have been featured in the original version of Star Trek Online.