A “sea lawyer” is someone who gives out free legal advice without the credentials to back it up.
As Marines, we encounter many challenges; some professional, some personal. Unfortunately, a lot of us have encountered legal issues either out in town or on base. The “sea lawyer” is a fellow Marine who has been through something similar, or knows someone who has, and begins telling you how to conduct yourself. In short, they are not attorneys and therefore should not be listened to. DO NOT listen to them.
The only person who you should be discussing legal matters with is the adjutant, a JAG officer at legal or, an attorney out in town. Don’t let yourself get into worse trouble than you’re already in, because you listened to a fellow Marine who lacked the credentials.
If you do happen to run into legal issues, consult professional legal counsel ASAP!