| Cover | Mar. 23, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 23, 2023 |
| Entity File Number | 001-39281 |
| Entity Registrant Name | TMC the metals Co Inc. |
| Entity Central Index Key | 0001798562 |
| Entity Tax Identification Number | 00-0000000 |
| Entity Incorporation, State or Country Code | A1 |
| Entity Address, Address Line One | 595 Howe Street |
| Entity Address, Address Line Two | 10th Floor |
| Entity Address, City or Town | Vancouver |
| Entity Address, State or Province | BC |
| Entity Address, Postal Zip Code | V6C 2T5 |
| City Area Code | 604 |
| Local Phone Number | 631-3115 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| TMC Common Shares without par value [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | TMC Common Shares without par value |
| Trading Symbol | TMC |
| Security Exchange Name | NASDAQ |
| Redeemable warrants, each whole warrant exercisable for one TMC Common Share, each at an exercise price of $11.50 per share [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Redeemable warrants, each whole warrant exercisable for one TMC Common Share, each at an exercise price of $11.50 per share |
| Trading Symbol | TMCWW |
| Security Exchange Name | NASDAQ |
