I think this is the one where you fight with the Seeq I believe. Have you spoken to the petittioneer for the hunt/ She will say it's located on the island where it rains the hardest, to get there you must cut down a number of trees, excuse for not being elaborate, but once you do, you will gain acess to the area where it is. The Seeq will join your party as a guest, but there will be other tortoises there not the Gil Snapper to make him appear leave and re-enter.
I hope that helped.
