Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2021	Jul. 26, 2021
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Document Transition Report	false
Entity File Number	001-39213
Entity Registrant Name	OneWater Marine Inc.
Entity Central Index Key	0001772921
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-4330138
Entity Address, Address Line One	6275 Lanier Islands Parkway
Entity Address, City or Town	Buford
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30518
City Area Code	678
Local Phone Number	541-6300
Title of 12(b) Security	Class A common stock, par value $0.01 per share
Trading Symbol	ONEW
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Common Class A [Member]
Entity Common Stock, Shares Outstanding		11,661,575
Common Class B [Member]
Entity Common Stock, Shares Outstanding		3,377,449