A sea trial is the marine equivalent of a test drive, crucial for assessing a vessel's performance before it is fully commissioned or sold. A sea trial or trial trip is the testing phase of a watercraft (including boats, ships, and submarines).It is also referred to as a shakedown cruise. A sea trial is totally out of the question. Is it OK to just get a marine survey done with the boat out of the water? Click here to learn more and purchase tickets! Sea trials are an important step within the boat buying process that allows you to take a boat for "test run. Sea trials completed with flying colors! Navy Region Legal Service Offices (RLSOs) provide legal assistance to eligible personnel and family members around the world to promote readiness. Sea trials are an important step within the boat buying process that allows you to take a boat for "test run.