If something is seamanlike, it is done in a way that is skilled and careful, like a good sailor would do it.
Seamanlike is a good thing. It means someone is doing something well, like a sailor.
Examples:
The sailor's knots were very seamanlike.
She moved seamanlike on the boat.
He did the job in a seamanlike way.
The seamanlike way he tied the rope impressed everyone.
Her seamanlike skills made her the best sailor on the ship.
He always works in a seamanlike manner.