Is the answer:
A safe
Spying has never been easier with me,
Safes contain sensitive information and can be helpful to spies
Boats have use of what's inside me,
Safes have locks, which is like the hull of the ship
Shout I do not, even when teeth may enter me.
The lock(s)/key have teeth
I'll be happy to share an interest
Find the right person, and all the stuff in a safe can be released
With many who look alike - unlike the rest,
It is in your best interest to show what is inside or how to open the safe with people you trust. In war, with people on your side
Guard against secrets... I do my best
Safes protect sensitive/valuable material from getting into the worng hands