No. Afloat is an adjective. It cannot be a preposition.
We won't be afloat for long!
it is bla bla afloat
Afloat was created on 2004-11-22.
The Borrowers Afloat was created in 1959.
Thunder Afloat was created in 1939.
The duration of Thunder Afloat is 1.58 hours.
the structure of the boat allowed it to stay afloat no matter what.
When the ship sank I used a lifebelt to help me keep afloat.
The duration of Alf's Button Afloat is 1.48 hours.
Alf's Button Afloat was created in 1938-07.
No, then is not a preposition. It is a conjuction.Than is a preposition.
The whale merely nudged our little boat and we were suddenly afloat, without a boat.