The US Navy has operated for years in densely packed shipping lanes, where friend had to be sorted from foe its entire existence.
In World War 2, it used PT Boats to patrol close in shore. Its called the "littoral" battlespace today but the theory was the same.
We would use our small boats to attack their small boats and keep them off our capital ships. It worked too. If you have the time, read about the history of these PT Boats in the war. They took on ships twice, sometimes three and four times their size and gave much better than they got. Additionally they did the other tasks that weren't as glamorous but important. They served as couriers, picked up downed aviators, inserted coastal watchers and special units, and even served as troop transports in a pinch.
Fast forward to the Vietnam war and the same problem reared its ugly head. How do you patrol a long shoreline filled with boats of all type and at the same time protect your ships AND provide fire support to forces ashore? There was no LCS, but the solution was almost magical. Again we saw small boats...this time called Monitors (converted landing craft that were fitted with extra armor and weapons) and helicopters nicknamed "Sea Wolves".
While I like the idea of "modern day Monitors" I don't think it would be accepted. They were able to absorb tremendous amounts of fire (to include B40 rockets...a variant of the RPG2) these slow moving boats would be too vulnerable on a modern battlefield.
Why am I bringing this up? Check out this Defense24 article...
American Navy carried out a series of shooting for small surface targets using modernized Longbow Hellfire anti-tank missile.The missiles have hit the arming of ships to the offshore activities of LCS.
The tests were organized in June. within the work on the next task SSMM module (Surface-to-Surface Missile Module) for ships to offshore activities. Task modules are generally permit the preparation of the watercraft to perform a specific mission.depending on the needs.
SSMM LCS ships will enable small and high-speed combat surface ships, the destruction of which does not pay to use expensive and large-type Harpoon anti-ship missiles. They will complement the fore cannon calibres 57 mm and rockets Sear (Google translate took a powder here for some reason).
During the shooting of rocket used remotely controlled surface targets HSMST (high speed maneuvering surface targets). Indeed they are the equivalent of high-speed boats posing a serious threat asymmetric for American ships.
Longbow Hellfire Missiles fired from a ship in the US Navy auxiliary "Relentless" hit seven to eight maneuvering targets. Tests simultaneous rally ended with three goals, which ultimately were hit.
SSMM modules have come to equip LCS ships at the end of 2017.
So a rapid firing 57mm cannon isn't enough to take care of small boats in Navy simms? I find that interesting in itself. If a rapid fire 57mm cannon that reaches out to about 10 miles can't do the job then something is definitely wrong. But putting that aside for a moment. What is the most effective modern weapon system to fight small boats?
Helicopters!
The US Navy should revive the Sea Wolf concept and seemed well on their way with the EFSS package adopted from the Army for the MH-60's. Taking it a step further, if the laser guided 2.75 rocket is adopted then you get more potential "kills" per sortie.
The LCS is undoubtedly under armed. Slapping short ranged (comparatively) missiles on it is not the answer....Hellfire is a great weapon, but not for the LCS.