If your character’s feet is floating when using Unity's humanoid mecanim animations, these are the 3 common reasons! See below!
1) Animations have root motion but your character ' apply root motion is off. (See image below)
2) Animations not bake to pose in inspector. Choose the correct setting depending on your gameplay. (See image below)
3) Foot IK not checked. Go to animator, select animation in animator and check foot IK. (See image below)