I did Sea School, they were great. They will teach you to pass the test. Takes alot of studying, colregs, safety, plotting etc. Passing the test doesn't make you a Captain, experience does. You do not need a license unless you take parties or charter. Ask Capt Jack, job sounds great, every day, every weather. Got mine a while ago. Worked for Tow Boat. Worked towing gig, do you know there aren't designated working hours? Any day, any weather, any hour.
Great course, learned alot. If you have the time and money, get you 6 pack, towing and sail endorsements. If you have time get the Masters, it is only a few other hours and about the same test.
Make sure the school can give you the test on prem, some only teach the school and you take the test at a CG facility.
The knowledge you get is worth it. Try working with a old salt like Jack for experience. I worked as a mate in Florida, sounded like a great job.
GOOD LUCK