Warmer currents carried Missy Mesophile* to exotic waters where her usual physiology offered no insulation at all. To add insult to injury, the aboriginal Psychrophiles weren't at all welcoming.
*Mesophile: "an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 15 and 40 °C (77 and 104 °F)." (courtesy of Wiki).
Psychrophile: "extremophilic organisms that are capable of growth and reproduction in cold temperatures" (courtesy of Wiki). Actually, they aren't just capable of growth at low temperature, but their growth ideal is at low temperature. Hence "psychro" (cold) and "phile" (loving).