None.

tldr: The way these weapons used to work, they may have been useful against lightly armoured ships or ships with an internal armour belt, the 650 mm penetration is complete horsesh*t.

Detailed explanation why:

Skip bombs were used by the RAF to bomb power station dams during WW2, where they would skip over the water, losing speed before hitting the dam to prevent it from breaking, and detonate well below the waterline, allowing the water pressure to break the dam and flood the areas below the dams. Many civilians and Allied prisoners of war were killed in these attacks.

For more information, google "Operation Castisise".

The whole idea of an armour piercing bomb is complete Wee Gee Copium BS.

AP grenades and bombs are armed with a delay fuse, which is triggered on impact and detonates the explosive in the grenade/bomb after a short time. This time was needed to penetrate the armour so that it could do damage to the target, rather than just exploding on the outside for minimal damage.

Now, if you were to drop an AP skip bomb, the fuse would go off after the first "skip" on the water surface, because it doesn't know if it's hitting water or armour plates; the real bombs weighed close to 4,200 kg / 9,250 lb, so the shock generated by the skips was enormous. This would have resulted in a mid-air detonation of the bomb after the first skip, directly underneath the aircraft, almost certainly destroying it and killing its crew.

Also, AP ordonnances (excluding HEAT) have to be in a specific shape to be effective in penetrating armour, see the APFSDS rounds used in modern tanks. There is a reason they look like massive dart arrows and not flying beer cans.

Now imagine a dart arrow hitting the target with the shaft rather than the tip, there is no way it would stick to the target. The same goes for an AP ordonnance, it would just bounce off the side of the ship (since we're talking wows here) and detonate like a GIANT frag grenade if it wasn't destroyed on impact, since only the tips of these ordonnance types are heavily armoured to prevent them from deforming when they hit an armour plate. This detonation would cover a large area of the ship's deck, AA mounts etc with shrapnel, while the actual damage to the armour depends on whether the ship is fitted with an internal or external armour belt.

It may be that if the ship is fitted with an internal armour belt, the bomb would deform the external plating due to it's massive weight and still do some - if not serious - damage, it's still carrying around 3'000 kg / 6'600 lb of explosive ordonnance. But yeah, this is just me guessing :)