Green’s Dictionary of Slang

1. drunk.

1641		T. Heywood Vertue of Sack 3: When my Braines are once aflote (Heav’n blesse us) / I think myself a better man than Croesus.
1730		J. Miller Humours of Oxford IV i: No more, no – no – more – my Brains are all a-float already.
1809		P. Freneau ‘On a Honeybee Drinking from a Glass of Wine etc.’ in Prescott & Sanders Intro. to Amer. Poetry (1932) 97: Go take your seat in Charon’s boat, / We’ll tell the hive, you died afloat.
1888		Missouri Republican 25 Jan. n.p.: His honor once more drank until, as an onlooker put it, his back teeth were well afloat [F&H].
1909		H. Lawson ‘The Horse-and-Cart Ferry’ in Roderick (1967–9) II 298: Always stick, when ‘afloat’, / To the passenger boat.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 217: afloat, drunk.
1933		‘William Juniper’ True Drunkard’s Delight.
1976		D. Ireland Glass Canoe (1982) 203: Alky Jack [...] was already afloat.

2. (Aus.) absent without leave.

1943

Sydney Morn. Herald 11 Dec. 7/3: If he absents himself without leave he is described as having ‘gone through,’ or more picturesquely ‘is afloat’.