Animating a character? (corpse floating in water)

[LDOriginal]

Is it possible? I've made a hallway with a window at the side and i would like to have a corpse float outside of it. Either passing by the window or being tangled up in something enabling the player to spot it. I noticed you could open upp the pose menu and adjust all of the joints for the character, wich is cool. But is there like a keyframe-sort of way to make the character move in a loop or something? Change the joint position/character position for every frame or is that something you do entirely in script? If so, how would one go about doing that? Thanks