Green’s Dictionary of Slang

1. (UK/US) a boat.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1935		A.J. Pollock Und. Speaks.
1942		D. Runyon in Star (Marion, OH) 31 July 6/8: Rhyming slang is not founded upon allegory unless we except a few similes such as ‘I’m afloat’ for boat [...].
1944		Maurer & Baker ‘“Aus.” Rhyming Argot’ in AS XIX:3.
1947		Cheltenham Chron. 22 Feb. 5/3: ‘I’m afloat,’ which is rhyming cant for a boat.

2. (also armour float) a coat.

1873		Sl. Dict.
1892		‘Doss Chiderdoss’ ‘The Rhyme of the Rusher’ in Sporting Times 29 Oct. n.p.: I was wearing a leaky I’m afloat / And it started to France and Spain.
1900		Sidney Truth 7 Jan. in Baker (1945) 269: I ’ad a brown I’m afloat, a green Jacky Lancashire in me lef’-’and sky, and tan daisy roots.
1910		Marvel 5 Feb. 3: ‘What is your “I’m afloat”?’ ‘Me coat,’ said Joe.
1923		Smith’s Wkly (Sydney) 11 Aug. 15/2: You can always drop a fur I’m afloat to a near- actress with a far-flung circle of admirers.
1935		Mirror (Perth) 14 Sept. 17/2: Coat: I’m afloat.
1960, 1975		Wentworth & Flexner DAS.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxii 6/1: armour float: Coat.
1969		S.T. Kendall Up the Frog 11: I’m takin’ me I’m afloat orf, its proper peas in the pot in ’ere.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 17: Armour Float Coat.
2002		Pete’s Aussie Sl. Home Page 🌐 I’m afloat: an overcoat.