A US Customs and Border Protection bulletin to shippers indicates no grace period for cargoes on the water at midnight on Saturday.

But a US Customs and Border Protection bulletin did provide a 51-day grace period for cargoes loaded onto vessels or planes and in transit to the US before 12:01am ET on Saturday. These cargoes need to arrive by 12:01 am ET (4:01am GMT) on May 27 to avoid the 10 percent duty.

https://www.aljazeera.com/news/2025/4/5/trumps-10-percent-tariff-takes-effect-raising-fears-of-global-trade-war