General synonyms:
* Drift
* Hover
* Suspend
* Glide
* Soar
* Move effortlessly
* Remain on the surface
Synonyms related to specific contexts:
* Sail (for boats)
* Blossom (for flowers)
* Rise (for prices)
* Circulate (for money)
* Dangle (for objects)
* Waver (for an image)
For a more specific answer, please provide the sentence or context in which you want to use a synonym for "float".