Stockholders’ Equity - Summary of Net (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Numerator:
Net income attributable to OneWater Inc	$ 10,715	$ 14,683	$ (1,624)	$ 3,544
Class A Common Stock
Denominator:
Weighted-average number of unrestricted outstanding common shares used to calculate basic net (loss) income per share (in shares)	16,313	14,593	15,700	14,571
Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract]
Diluted weighted-average shares of Class A common stock outstanding used to calculate diluted net (loss) earnings per share (in shares)	16,444	14,891	15,700	14,835
Net (loss) earnings per share of Class A common stock – basic (in usd per share)	$ 0.66	$ 1.01	$ (0.10)	$ 0.24
Net (loss) earnings per share of Class A common stock – diluted (in usd per share)	$ 0.65	$ 0.99	$ (0.10)	$ 0.24
Class A Common Stock | Employee Stock
Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract]
Restricted stock unit and employee stock purchase plan (in shares)	11	1	0	0
Class A Common Stock | Restricted Stock Units
Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract]
Restricted stock unit and employee stock purchase plan (in shares)	120	297	0	264