[alamwuhk2a]

I found some interesting information.
The Walter boot use some special power to drive under water. The Walter Turbine. Normally, a boot use battery to drive under water, however, use oxygen and fuel to drive under water. The oxygen comes from hydrogen peroxide. Thus, the Walter boot can actually 'run' at 24 kts submerged and have a good range.
Unforturnately, in SH3's system, it may not be possible to use the normal fuel underwater and remove the battery system. I can only change the battery into 'Walter battery' and the electrical engine into 24kts.

Woof, if you are happy with this, it is easy to use the XXI model and change XXI into XVIII.