@TheMouse yes, the vtol nozzle can still function even if it is submerged in water, as long as the blasto vtol is not submerged, when the submarine is on the surface of the water the propeller can still rotate, as long as it is not completely submerged in water, so it will increase the speed of the submarine when the submarine dives, the propeller cannot function and the speed of the submarine will decrease, this can be overcome by increasing the number of vtol nozzles.

@Tipo4062
Hmm. Not sure then. The other option is just to use a VTOL nozzle hidden inside, with the prop just for show. You can put the VTOL jet somewhere above water hidden, and it should work well.

@TheMouse I've set the chord scale to 12-13 but it still doesn't work, I'll try again later. For your information, I have succeeded in making a submarine that can move even while diving, using @Walvis's method. And thank you for the upvote.

Set the chord scale to 15 or so.