Green’s Dictionary of Slang

alcohol, liquor; thus as phr. on the ooze, drinking or drunk.

1932		‘P.P.’ Rhy. Sl. 5: ‘’Strewth, yer “King Death” don’t arf “Pen and Ink,” been on the “River Ouse?”’ – ‘not ’arf’.
1939		Dly Mirror (London) 2 May 22/1: [cartoon caption] Ah — that’s Soho slang, Jo! ‘Snouty’ means tobacco, ‘River Ouse’ booze [...] and ‘band of hope’ is dope.
1962		R. Cook Crust on its Uppers 82: The Cure, which was down to mental angst as much as the river ooze.
1984		‘Derek Raymond’ He Died with His Eyes Open 71: Down to being into the river like he was, I believe he’s by way of having a nervous breakdown right now.
1984		Partridge DSUE (8th edn) 829: [...] since ca. 1920.
1989		J. Morton Lowspeak 122: River – drink.
1992		R. Puxley Cockney Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.