Are there really `black holes' in the Atlantic Ocean?

In this letter we point out some interpretational difficulties associated with concepts from General Relativity in a recent article which appeared in J. Fluid Mech. 731 (2013) R4 where a Lorentzian metric was defined for turbulent fluid flow and interpreted as being analogous to a black hole metric. We show that the similarity with black hole geometry is superficial at best while clarifying the nature of the black hole geometry and the work above with some examples.