I use a c_trace from player.x to player.x in order to check if he's into a passable entity to make the player swim. It worked perfectly on A7 and the previous A8 versions, but in the last 8.10.1 the player instead of swim simply falls to the ground like if c_trace doesn't detect anything. The water checker is a passable model with FLAG8.

This is the code I use to check:

I don't think that this can work, at least not with c_trace. You need to cast a ray for hitting a polygon, but at a length of 0 the ray can not hit anything.

In A6, there was a special mode to detect passable water blocks, but as to my knowledge this also required that the ray hit the surface of that block. I'm not sure though, this was quite long ago.

Since A7, we recommend using terrain for water. You can then simply check if the player is in water or not by comparing his position with the water surface. c_trace was not changed since A7.

Ok, I will do it what way, then, as a curiosity, why that worked for me on previous versions?

You can use terrain as a passable and invisible entity for water, and use another model, block, or asset to represent the visible water.

just use the passable_ent pointer with c_trace. If the trace origin or end is inside the passable terrain, the passable_ent pointer is set to the terrain. You could set one of the skills of the terrain, and have your script check this skill to detect is as water.

(though I wish there was a way to detect when a player is inside a solid mesh / block for detecting if it accidentally became embedded in a solid after movement...)

I've done it checking the relative position of the player to the water terrain, in order to check if the player is down and into its limits and then set a entity pointer of the water.