Two versions of the warships were sped into production to meet the Navy‘s goal of an affordable, fast ship to operate in shallow coastal — or littoral — waters.

The ships, which are capable of topping 50 mph, utilize steerable waterjets instead of propellers and rudders to operate in shallow water.

They also are built to be equipped with swappable mission modules for surface warfare, anti-submarine duty or mine removal. That’s in contrast to larger, multi-mission ships like the 610-foot Michael Monsoor, a Zumwalt-class destroyer christened Saturday at Bath Iron Works.

But the gee-whiz factor was overshadowed by concerns over growing costs — the latest versions cost $482 million to $563 million apiece — along with criticism by the General Accounting Office that the warships were too lightly armed and too lightly armored.