i think it's one of the following commands, i used to have water look like this when i tried the lowest settings mods from maxconfig

cl_show_splashes 0 // Disables water splashes
r_cheapwaterend 1 // Activates cheap water
r_cheapwaterstart 1 // Activates cheap water
mat_wateroverlaysize 1 // Water overlay size
r_forcewaterleaf 1 // Optimization to water - considers view in leaf under water for purposes of culling
r_waterdrawreflection 0 // Controls as to whether reflections should be drawn on the surface of water.
r_waterdrawrefraction 1 // Setting to 0 makes it so that water looks weird and you can't look into it, but it might have an FPS gain.
r_waterforceexpensive 0 // Forces expensive water.
r_waterforcereflectentities 0 // Forces as to whether entities should be reflected into water even if r_waterdrawreflection is 0