sleeping in a ship
Literally sleeping aboard a vessel, often with a sense of floating on the water.
On a ship journey, sleeping while feeling the rocking of the waves isn't so bad.
sleeping on the water's surface (of a bird)
Describes waterfowl resting while floating.
Ducks are sleeping on the surface of the pond.
restless sleep
Sleep that is light and easily disturbed, as if floating.
With worries on my mind, I had a restless sleep last night.
casually sleeping together (e.g. unmarried couple)
Implies an informal, possibly transient co-sleeping arrangement, often with romantic or sexual connotations.
In old tales, unmarried men and women casually sleeping together is sometimes depicted.
Standard kanji spelling.
Irregular okurigana usage; less common.
Compound of 浮き (uki, 'floating') + 寝 (ne, 'sleep'). The exact historical derivation is uncertain, but the word literally means 'floating sleep'.