A spurred tortoise was found trapped near North Point Ferry Pier and later confirmed dead after being rescued by firefighters.
The case has been classified as animal cruelty.
The tortoise measured about 30 centimetres in length.
Firefighters wearing life jackets climbed onto the pier to examine the animal and document the scene.
Police received a report about the case at around 4 p.m. Firefighters and officers from the Agriculture, Fisheries and Conservation Department arrived at the scene.
The species is a desert-dwelling, herbivorous land tortoise and cannot survive in water.