What if the souls series had swimming? Would it be a good idea?
Probably not. You’d need to make a totally new set of animations and mechanics for it and it wouldn’t really emphasize what the series is established on.
Now a new game based on swimming and underwater combat in the souls style, sure, that might be interesting.
How would you design Deep Souls/Dark Swims?
Gonna go with the title: Shark Shoals: Prepare to Dive
Could hold sprint or another buttons while standing still to charge a jump upwards, could have extra long fall distances with no fall damage, only bottomless pits kill.
Maybe let you mash the button to hover or swim upwards varying amounts at the cost of stamina. Could make you also move a bit faster on the lateral plane, similar to jumping in water in Mario.
R1 in the air/water could be a strong high attack and R2 could be a weak low attack. Or vice versa. The idea should be that one of these is weak and one is strong so you want to get enemies into a certain range above or below you to use your better attacks. Could be per-weapon too, with R1 just being high attacks and R2 just being low attacks when up in the water. During attacks, your Z axis movement could be slowed until the attack ends to make attacks a bit more committal and less hectic. This also means attacks can double as air stalls.
Blocking could be purely based on relative angles, like it is on the ground, instead of getting all complicated with enemies going over your head or under you.
A basis like this could allow for a lot more verticality than souls levels already have, and something resembling the souls combat system in open water, with a unique twist that takes advantage of the fact that you’re moving in open 2d space.
Locales could be coral reefs, sunken ships, trenches, etc.
Tough part is the enemies, Souls series has never done so well with free flying enemies. You’d definitely need enemies that work as well in open water as the Gargoyles in Demon’s Souls. Having the enemies be all or mostly fish would also be troublesome, because fish don’t telegraph attacks so well. Would need to get creative with ocean life, or adapt land creatures to the sea. I can see a lot of enemies ending up like the dogs and wolves: Running at you then doing a bite attack when close, and that would suck.
This also means developing enemies with movement patterns up and down in the water that are more complex than simply moving at you. Souls enemies frequently strafe around you on the ground and more interesting reactive movement patterns would need to be worked out for Z-axis movement. A 2d platformer game might be helpful here.
I think the idea has potential and it could be a relatively simple conversion, depending on how it’s handled.