Disable underwater reverb of 3D floors

[SPZ1]

The reason I'm asking is because I think using the swimmable 3D floor is the best way to make a ladder.

[Enjay]

Being able to disable underwater reverb on a case-by-case basis would be useful (I think you are correct that it can't be done ATM, other than an overall CVAR). It has been asked about before, and the reason has usually been to make a ladder. There are also other things, like the fact that you can "drown" on your ladder, that needs to be accounted for too.

Setting a sector to have low gravity could be a possible alternative?

Have you tried Jekyll Grimm Payne's ladder?

There's also AFADoomer's ladder

Personally, I use a modified version of the ladder that Boondorl made for "Dooming the Bar". I find it really good and you can set the height to whatever you want. The player latches on when you approach the ladder (but it's easy to disengage if you want to). I tweaked a few minor things to my preferences and added the ability for it to play a foot-on-rungs sound periodically while you are latched on and either moving up or down (basing it on code that phantombeta gave me for another actor entirely). To me it feels very much like a modern game style of ladder. I know that Boondorl was planning on making his own portable version of it (don't know if that's still the plan). So, I wouldn't distribute my modified version without his agreement.

However, here it is in action.

(The footsteps don't sound anything like as loud in a normal map with music and lots of other things going on.)

The ladder actor is invisible and I use a separate no-collision actor with a model of suitable size, or a texture, as is appropriate. Personally I prefer that to a ladder that has a built-in model because it gives me flexibility.

[SPZ1]

It seems a new 3d floor type which both doesn't drown the player and disables the reverb would be ideal.

[Enjay]

Sure, I was just suggesting alternatives that might suit you seeing as how what you want doesn't already exist.

It might be worth opening an issue on the UZDoom GitHub pages if you want to submit the idea for consideration for UZDoom.