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, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Numerator:
Net income (loss) attributable to OneWater Inc	$ 11,673	$ 10,715	$ (8,939)	$ (1,624)
Class A Common Stock
Denominator:
Weighted-average number of unrestricted outstanding common shares used to calculate basic net (loss) income per share (in shares)	16,618	16,313	16,588	15,700
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)	16,954	16,444	16,588	15,700
Net (loss) earnings per share of Class A common stock – basic (in usd per share)	$ 0.70	$ 0.66	$ (0.54)	$ (0.10)
Net (loss) earnings per share of Class A common stock – diluted (in usd per share)	$ 0.69	$ 0.65	$ (0.54)	$ (0.10)
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)	3	11	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)	333	120	0	0