Pokémon are all over the world in Pokémon Go, and to find the new ones when they release to the game is all about traveling the world to find them in their respective ecosystems. Some of these Pokémon are at the beaches, and others are in the middle of forests, matching their ideal lifestyle, given what type of Pokémon they are. The rarer ones are usually hatched from eggs, meaning you can only receive them by meeting the walking requirements and hatching them.
For those on the lookout for Sandile, you won’t be able to find it at a beach or on a sunny day. Instead, you need to receive it from a specific egg, a strange egg commonly called a red egg due to its color pattern. Unlike traditional eggs that you receive for spinning a Poké Stop or Gym Disc or the one you get from friends who send you gifts, a strange is only obtained from defeating one of the Team Rocket leaders. You need to fight Sierra, Cliff, or Arlo to earn the egg. You also need to make sure that you have a spare egg slot in your inventory, or you will not receive the egg.
Once you have the egg, it has the longest distance requirement for you to hatch it. It takes 12-kilometers for you to hatch it, and once you place it in an incubator and meet that requirement, you can see what’s inside of it. It won’t always be a Sandile, but that’s the only way to capture it, so you may need to battle multiple Team Rocket leaders to try and catch it. Eventually, after you gain enough candies, you can evolve it into a Krookodile.