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, 2020 USD ($) Store State Brand $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)
Description of the Business [Abstract]
Number of stores operating | Store				61
Number of states in which stores operating | State				10
Number of top brands | Brand				10
Public Offering [Abstract]
Proceeds from initial public offering | $				$ 59,234	$ 0	$ 0
Payment in exchange for surrender of preferred distribution right | $			$ 3,200
Organizational Transactions [Abstract]
Common stock, conversion basis				one-for-one
Preferred stock, shares authorized (in shares)				1,000,000	1,000,000
Preferred stock, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
OneWater LLC [Member]
Principles of Consolidation [Abstract]
Ownership interest				69.40%
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)				10,391,661	0
Organizational Transactions [Abstract]
Common stock, shares authorized (in shares)				40,000,000	40,000,000
Common stock, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Conversion of stock, shares converted (in shares)				1
Total number of shares reserved for issuance (in shares)			1,385,799	1,385,799
Common Class A [Member] | Legacy Owners [Member]
Organizational Transactions [Abstract]
Number of shares issued for each unit redeemed (in shares)				780,213
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)				4,583,637	0
Organizational Transactions [Abstract]
Common stock, shares authorized (in shares)				10,000,000	10,000,000
Common stock, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Conversion of stock, shares converted (in shares)				1
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
Organizational Transactions [Abstract]
Common stock, par value (in dollars per share) | $ / shares			$ 0.01
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)	475,630	425,000
Common stock, shares issued (in shares)		2,745,868
Period granted to underwriters	30 days	30 days
Number of additional shares intent to purchase by underwriters (in shares)	387,458	475,630
Sales Revenue [Member]
Description of the Business [Abstract]
Concentration risk percentage				41.10%	40.40%	40.00%
Sales Revenue [Member] | Malibu Boats, Inc [Member]
Description of the Business [Abstract]
Concentration risk percentage				16.20%	15.90%	13.40%