Stockholders’ Equity - Summary of Net (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Numerator:
Net loss attributable to OneWater Inc	$ (12,901)	$ (368)	$ (20,612)	$ (12,339)
Class A Common Stock
Denominator:
Weighted-average number of unrestricted outstanding common shares used to calculate basic net (loss) income per share (in shares)	16,614	15,968	16,574	15,393
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)	16,614	15,968	16,574	15,393
Net (loss) earnings per share of Class A common stock – basic (in usd per share)	$ (0.78)	$ (0.02)	$ (1.24)	$ (0.80)
Net (loss) earnings per share of Class A common stock – diluted (in usd per share)	$ (0.78)	$ (0.02)	$ (1.24)	$ (0.80)
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)	0	0	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)	0	0	0	0