I have the Arras and Aminens myself. I know how powerful these boats are, especially at a BR of 3.0.
These boats have been plaguing the coastal gameplay thanks to the event.
The ammo rack is deep within water, and it basically has a blue water damage model which means no coastal weapons other than torpedo and rockets can tackle it.
The L9059 is actually balanced; while powerful, it’s hull can take damage from even 40mm. The Arras relies on module damage.