frío como un pescado 18
COLD AS A very low temperature FISH. Fish are cold-blooded and therefore their body is at a temperature similar to that of water. If there were ever warm-blooded (tropical) fish, these became extinct because of the high demand for energy required to maintain the constant high body temperature and the great heat dissipation of being in a cold or icy environment. The correct phrase should be cold as a fish, for all dead animals are cold after a while.