As per the government Travel Advisory published on December 8th, all vessels MUST contact Antiguan authorities on Channel 16 prior to arrival where they will be directed to a specific clearance port and scheduled for the Health Authority COVID check.
You cannot go ashore until duly authorized by Health.
If you do, you will be breaking the law.
Several visitors have tried this deviation and been given a warning. That may change if Antigua experiences a spike in infections.
Once the Health Authority is happy with your tests and declaration, you can proceed ashore to clear in with Customs and Immigration.