浮 (fú) is the basic verb for 'to float', typically on a liquid surface (e.g., wood on water). It contrasts with 飘 (piāo), which emphasizes floating in the air with a light, drifting motion, and with the more formal disyllabic 漂浮/飘浮 (piāo fú), which can be used for both water and air. Note that 浮 also has other meanings (superficial, temporary) outside the verb sense.