Stockholders’ Equity - Summary of Net (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Numerator:
Net loss attributable to OneWater Inc	$ (11,971)	$ (7,170)
Class A Common Stock
Denominator:
Weighted-average number of unrestricted outstanding common shares used to calculate basic net (loss) income per share (in shares)	14,831	14,540
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)	14,831	14,540
Net (loss) earnings per share of Class A common stock – basic (in usd per share)	$ (0.81)	$ (0.49)
Net (loss) earnings per share of Class A common stock – diluted (in usd per share)	$ (0.81)	$ (0.49)
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
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