The Hunt for the Croakadile can be obtained after the events at the Tomb of King Raithwall and the Shiva airship once the team arrives back in the city of Rabanastre. The Croakadile is one of the easier hunts that you can complete.
Travel to the Giza Plains during the rainy season and visit the Nomad Village. Sadeen is standing right in the middle of the village.
Travel to the Starfall Field which is in the southwest corner of the Giza Plains. Cross the wooden bridge heading southward and the Croakadile will automatically jump out.
The Croakadile fight is one of the easier battles as there is very little strategy involved. The Croakadile has a fair bit of HP and hits fairly strong but there are no surprises in the battle aside from this. It will also use Renew and Growing Threat abilities to increase the amount of HP and damage it does. Just utilize your Quickenings or your new Esper, Belias, to help defeat it if you are having trouble.
A video of the battle in the Zodiac Age version is included below:
Return to Sadeen in the Nomad Village to obtain your rewards which include 1,200 gil, a Serpent Rod and a Teleport Stone. You will also receive a Ring of the Toad which needs to be taken to Elder Brunoa back in the Nomad Village during the Dry season. Check out the Rain in the Giza Plains section of the tips and tricks area for more information on how to switch between the rainy and non-rainy seasons.