I found code like one below to find water on every map:
PHP Code:
// Find water on map and save its ids
new Ent = engfunc( EngFunc_FindEntityByString, -1, "classname", "func_water");
while((Ent = engfunc( EngFunc_FindEntityByString, Ent, "classname", "func_water")))
{
if(!gWaterExists) { gWaterExists = true; }
gWaterEntities[Ent] = true;
} // And later check in addtofullpack and hide with set_es()
But since many water blocks on maps has only liquid texture, this way is insufficient. So how to fetch them all?