Where to find water hydro pump in emerald?

after you beat the elite four go to the safari zone and then you go to the place with the gps Pokemon and go to the spaces in the grass and then i forgot the grass place i got it so it is in the grass place somewhere and you find the TM hydro pump and you could also find it by finishing the hoenn pokedex and then go to professor birch and when he talks to you about the national pokedex that he will give you talk to him again and then he will say "oh did i forget to give you this" and he will give you the TM hydro pump i hope this helps you.