Feel like this undermines the entire weight system. You're able to swim on 1.13 and the drowning does not prevent this.

Tried increasing the drowning rate in the config?

I guess that's a solution, already tried doubling it and have no trouble out swimming it... Guessing it needs to be a rather large number now...

Default setting is supposed to be difficult, but not impossible to swim out of (with pre-1.13 movement). Let me know what works similarly for 1.13

Was still able to swim with the number at 1000, guessing this mod is starting have many easier methods to doing things due to the new changes in Minecraft... I played this years ago when the developer was hosting a server for it and it was actually hard back then, but now it seems like a lot of the things can just be bypassed by other means now.

Able to surface, or just swim? It never prevented lateral swimming.

That being said I could try to just disable swimming altogether if too heavy

Feel like disabling the ability to toggle swimming would be the right solution? The other way around it would be that you can use riptide enchant to shoot up and out of the water, I honestly would help out if I had any experience with Minecraft plugin making but have no idea how to quickly get set up with it.