The phrase "float in the sky" is correct and usable in written English.
You can use it when you are describing something that is being suspended in the air, as in, "The hot air balloons floated in the sky, the bright colors dazzling in the sunlight."
It is particularly beautiful at night, when the floodlit Wat Chom Si temple appears to float in the sky, and lanterns litter the grounds.
In the game's seemingly deserted world, islands float in the sky, huge fish leap gracefully through the ocean, and enormous buzzing bugs hover over gigantic flowers.
Mr. Holroyd refers to it, a bit melodramatically, as "a place of fantasy that seems to float in the sky," a spot that "answers the need for make-believe in all our lives".
There were factory smokestacks, with immobile puffs of bluish-gray smoke above them, and beyond, through the smoke, he could just make out the contours of Moscow's skyscrapers, with red warning lights on the tips of their spires, and these lights seemed to float in the sky.
He can also be funny (a transfer of Santa Claus stuck to a window seems to float in the sky beyond); macabre (an arm holds up a paper target in a shooting range, the well-grouped bullet holes piercing the silhouetted head); and formally reserved (rolls of printed fabric, depicting a bucolic pattern of fox-hunters).
Detached skyscrapers float in the sky, cityscapes face their mirrors, and illuminated buildings become a geometric matrix of lights.
The war between the drug cartels has resulted in killings north of the Rio Grande but that is not a recent development and it is unclear how having the intrusiveness of big brother's eye-in-the-sky floating overhead might do anything to prevent that bloodshed.
Or was it the unholy-Russian-Empire-in-the-Sky that floats above the kleptocratic Kremlin of Vladimir Putin?
A hawk floated in the sky like an ash.
