Swampert is the evolvesion of mudkip which is one of the three pokemon you can pick to start out with in the beginning of the game therefore you cannot get him unless you pick mudkip at the beginning of the game
The best water Pokemon in Pokemon emerald I believe is Kyogre. kyogre is probably the stongest but i prefer a swampert if you don't like legenderies
The starter Pokemon for Emerald are Torchic, Mudkip, and Treecko. Their second stages are Combusken, Marshtomp, and Grovyle. Their final evolutions are Blaziken, Swampert, and Sceptile.
Kyogre
Level 36.
Train a mudkip to level 36.
Swampert or Wailord.
Swampert's ultimate moves are endeavor, earthquake, hammer arm, and mud bomb
Sceptile is way better than Breloom. Swampert is better than Sharpedo, Swampert is also a Ground type.
Endeavor is a move that can be learned by certain pokemon like Swampert and so on.
metagross salamence flygon blaziken swampert sceptile
CUZ ITS AN HM YA Cookoo
sceptile or a blaizeiken or a swampert