Stockholders' and Members' Equity, Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 30, 2022	Sep. 30, 2021
Stockholders' and Members' Equity [Abstract]
Share repurchase program authorized amount					$ 50,000
Share repurchase under program (in shares)			0
Numerator [Abstract]
Net income attributable to OneWater Inc.	$ 55,977	$ 34,503	$ 112,293	$ 62,765
Common Class A [Member]
Earnings (loss) per unit attributable to common interest holders [Abstract]
Common stock, shares outstanding (in shares)	14,133,130		14,133,130			13,276,538
Denominator [Abstract]
Weighted-average number of unrestricted outstanding common shares used to calculate basic net income per share (in shares)	14,133,000	10,976,000	13,791,000	10,884,000
Effect of dilutive securities [Abstract]
Restricted stock units (in shares)	379,000	365,000	414,000	259,000
Diluted weighted-average shares of Class A common stock outstanding used to calculate diluted earnings per share (in shares)	14,512,000	11,341,000	14,205,000	11,143,000
Earnings per share of Class A common stock - basic (in dollars per share)	$ 3.96	$ 3.14	$ 8.14	$ 5.77
Earnings per share of Class A common stock - diluted (in dollars per share)	$ 3.86	$ 3.04	$ 7.90	$ 5.63
Common Class B [Member]
Earnings (loss) per unit attributable to common interest holders [Abstract]
Common stock, shares outstanding (in shares)	1,429,940		1,429,940			1,819,112