Boat is Mashua
What is the difference between wangu and yangu?
Wangu is "my" for singular nouns and yangu "my" for plural nouns.
Is not a mtubwi also a boat?
Do you mean mtumbwi, or mtubwi? Either way, I don't know the answer, but I cannot find a Wiktionary entry for mtubwi, and the one for mtumbwi only gives "dugout canoe" as a definition.
That is apparently kayaki