Although Equestria is now uninhabitable, Sea Swirl is largely happy with her current conditions. She's on a tropical island, surrounded by water and sea life galore. Nothing could make her want to leave.
Well, except her fellow creatures regressing and turning on each other. Hence the key word "largely".
However, when a creature once only heard of in stories comes forth and reveals herself, she sparks a new friendship and offers Sea Swirl a chance at keeping her life with a simple spitball that will change everything.
An entry into the Tropical Post-Apocalypse Story Contest.
CW: The complete and utter butchering of aquatic science. Probably. My Google-fu is not good. You have been warned.