There are two concepts in circulation:
1. a high-speed warship with much of its hull submerged but otherwise has a functional superstructure with defense weapons and radar
2. other is almost completely submerged arsenal ship with two conning towers.
Both ship designs could displace roughly about 20,000 tons at full load.
These warships could carry hundreds of guided missiles.
The arsenal ship would have most of its hull inherently submerged, with only the bridge and a few other parts of the ship above the waterline which reduce the radar cross section. This would be in situations where the ship is hiding or trying to protect itself.
But when traveling with a high-speed naval task force, the arsenal ship will sacrifice stealth to use its flat hull bottom to hydroplane at high speeds, cutting across the waves like a speedboat or amphibious armored vehicle.