Maritime Academy schooling, or US Coast Guard, or US Navy are routes to becoming a ship crew member, then mate, then a captain. But it takes decades of experience for large vessels (over 50 feet).
Our geophysical vessel in Caribbean 49 years ago had a reserves US Navy commander as captain. He was strict, but very knowledgable. US Naval Academy graduate. Was uneventful mostly, a little stormy (hurricane season). But one day there was smoke everywhere and the engineer came running up from below. He was almost ready to pull the fire extinguishers when assistant engineer said it was only the diesel engine's supercharger bearings burning up. It was a new one, just installed and had not been cleaned properly. Its oil lube holes were still plugged. Just a lot of smoke, but when you are 50 miles from anywhere or anyone, pretty scary.
My neighbor's son did the academy route, served at several levels, now he is a captain for various sized yachts in Mexico, Caribbean and Mediterranean Seas.