Flash A water

Run forward (hold W), and as you move, jump-throw: hold left click, then jump and let go at the same moment.

From A main. Stand against the wall at the corner. Aim at the small window on the building through the arch.

Practice (with sv_cheats 1): setpos 1604.60 1446.48 -145.97;setang -25.81 -90.93 0