The first challenge
A missile boat, capable of carrying at least 2 anti-ship missiles. The boat may be extended in length and draft for this model only.
A torpedo boat, capable of launching modern torpedos for shore defence from submarines.
A sub-chaser, which is armed with guns and depth charges
And a hydro-graphic support ship designed to support scientific research (for those not inclined to make military boats)
So yes, one or all of these drawings, based on the same hull is the challenge. Remember there will be no winner and their is no contest, it is simply up to your creativity and style, and for fun.
It's weird, yes, and totally unrealistic in some points (torpedo launching, etc.) but... some tasks such a fast patrolling vessel either near the sea coast, or in a river or even on a lake, it can indeed come up with. I draw a catamaran 12m of length, as required, .30 m of draft, as required also. It has a cabin in the middle part joining the two hulls, on which rear part are fixed three Honda four stroke 160 hp outboard engines. The vessel has a searchlight and a navigational radar with the capability of identifying other vessels (provided they have the necessary hard- and software installed).
In the front part of the middle hull there is a 7.62mm machine gun installed on a tripod as well as on the rear of the two main hulls, this makes three MG in total. The vessel has also four portable MBT LAW shoulder missile launchers and eight small anti-ship missiles for each one, all produced by Saab Bofors Dynamics in Sweden. This is primarily an anti-tank system but I see no reason why it could not be used against naval targets at close range (not more than some 800 meter). "Guidance is obtained using predicted line of sight (PLOS)
; for a moving target, the gunner maintains tracking for three seconds, training the missile's guidance electronics to compute the target's angular speed. After launch the missile flies autonomously to the target making the necessary corrections according to the data acquired by the tracking. It is unnecessary for the gunner to consider the range to the target. After launch the missile's position in its trajectory always coincides with the target irrespective of range." (Wikipedia)