Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2025	Aug. 13, 2025
Document And Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2025
Entity File Number	001-39281
Entity Registrant Name	TMC the metals Co Inc.
Entity Incorporation, State or Country Code	A1
Entity Tax Identification Number	00-0000000
Entity Address, Address Line One	1111 West Hastings Street, 15th Floor
Entity Address, City or Town	Vancouver
Entity Address, State or Province	BC
Entity Address, Postal Zip Code	V6E 2J3
City Area Code	888
Local Phone Number	458-3420
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
Entity Common Stock, Shares Outstanding		406,392,921
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001798562
Amendment Flag	false
Common Shares, without par value
Document And Entity Information
Title of 12(b) Security	Common Shares, without par value
Trading Symbol	TMC
Security Exchange Name	NASDAQ
Redeemable warrants, each whole warrant exercisable for one Common Share, each at an exercise price of $11.50 per share
Document And Entity Information
Title of 12(b) Security	Redeemable warrants, each whole warrant exercisable for one Common Share, each at an exercise price of $11.50 per share
Trading Symbol	TMCWW
Security Exchange Name	NASDAQ