I built all my boats with terminals made by Ancor(now marinco), tin plated
The trick is the inside of the insulator is coated with hot glue adhesive.
After you crimp, heat, then you have a fully sealed connection.
I have had things pull so hard that the ring of the terminal broke and the wire never pulled out of the crimp.
Adhesive Lined Heat Shrink Ring Terminals | Marinco
http://www.marinco.com/productline/adhesive-lined-heat-shrink
I think 3M makes them also (3M Scotchlock Terminals ) but I don't think they are tin plated.