Tavo for Juan take a Corphish that evolves after it defeats a member of the Spheal line, Feebas line, Barboach line, Goldeen line and Luvdisc (basically the Wallace's old team), using only Water-type moves. (I think in Emerald the Cooltrainer with Milotic is gone so just be sure to catch Corphish before fighting the Fisherman with the Feebas, unless you want to find a wild Feebas on your own)
Name it Riptide.
aloquesada take a Shuppet that evolves after it defeats the Hex Maniac with the Sableye at the top floor of the Mt. Pyre building.