The "classic effects" option added in the Half-Life 2 20th Anniversary Update, located in the "Advanced.." submenu in the options menu's "Video" tab does not change the toxic water splashes back to their original 2004 release counterparts.
The old toxic water splashes look similar to the regular water splashes that went unchanged throughout the game's life, but coloured yellow instead of white.
The "classic effects" option added in the Half-Life 2 20th Anniversary Update, located in the "Advanced.." submenu in the options menu's "Video" tab does not change the toxic water splashes back to their original 2004 release counterparts. The old toxic water splashes look similar to the regular water splashes that went unchanged throughout the game's life, but coloured yellow instead of white.