Occasional, only tribal nudity, women showing breasts in ceremonial dances and everyday life, child buttocks (in distant as children in tribes wave far away), etc. This only happens in Papua New Guinea Episode. This is cultural rather than sexual or erotic.
In the Papua New Guinea episode, both Tims decide to be part of the ceremonial village dance. They wear costumes that reveal their torso, abdomen, all of their legs, and their buttocks. Tim Charody is the one that you see the most naked. They are all naked except for a small piece of cloth covering their genital area. This isn't sexual, and children can watch without parental guidance.
Men seen shirtless.
Tims open their towels covering their private parts and show their genitals, but not facing the camera. This is not sexual, and is only something natural that people do in their room.