Description of Company and Basis of Presentation (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Sep. 29, 2020 shares	Sep. 22, 2020 USD ($) $ / shares shares	Feb. 11, 2020 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) Store Brand State $ / shares shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)
Description of the Business [Abstract]
Number of stores operating | Store				70
Number of states in which stores operating | State				11
Number of top brands | Brand				10
Public Offering [Abstract]
Proceeds from initial public offering | $				$ 0	$ 59,234	$ 0
OneWater LLC [Member]
Principles of Consolidation [Abstract]
Ownership interest				87.90%
Legacy Owners [Member]
Public Offering [Abstract]
Payment in exchange for surrender of preferred distribution right | $			$ 3,200
Common Class A [Member]
Public Offering [Abstract]
Common stock, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Common stock, shares issued (in shares)				13,276,538	10,391,661
Common Class B [Member]
Public Offering [Abstract]
Common stock, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Common stock, shares issued (in shares)				1,819,112	4,583,637
Initial Public Offering [Member] | Common Class A [Member]
Public Offering [Abstract]
Number of shares issued (in shares)			5,307,693
Common stock, par value (in dollars per share) | $ / shares			$ 0.01
Number of shares issued on exercise of options (in shares)			692,308
Share price (in dollars per share) | $ / shares			$ 12.00
Proceeds from initial public offering | $			$ 59,200
September Offering [Member] | Common Class A [Member]
Public Offering [Abstract]
Number of shares issued (in shares)		3,170,868
Share price (in dollars per share) | $ / shares		$ 20.00
Proceeds from initial public offering | $		$ 8,100
Stock sold (in shares)		425,000
Common stock, shares issued (in shares)		2,745,868
Period granted to underwriters		30 days
Number of additional shares intent to purchase by underwriters (in shares)	387,458	475,630
Sales Revenue [Member] | Product Concentration Risk [Member] | Top Ten Brands [Member]
Description of the Business [Abstract]
Concentration risk percentage				42.90%	41.10%	40.40%
Sales Revenue [Member] | Product Concentration Risk [Member] | Malibu Boats, Inc [Member]
Description of the Business [Abstract]
Concentration risk percentage				17.00%	17.00%	15.90%