Hmm, I suppose.  I'll do it for sure, just to have another piece of cool looking paper to show the harbor master.  It's just that I can go for helmsman over there in about 4-5 years.  That'll let me do even more, and then the rank of sea captain and icebreaker captain. 
As for the question of the tanker, yes, I can.  It says any boat with or without mechanical propulsion inland.  That includes supertankers.
-Penguin