Well, in terms of better water types, Swampert is a Electric type killer with Hydro Pump. Feraligatr is a Dragonite Killer, and has a wide variety of moves. Lapras can use ice beam to defeat dragos, and has some good defense and spatk to back it up. Starmie is a KILLER with the right stats. Basically, your personal preference. This is the short version of what im telling.
Swampert has a pretty nice moveset, EarthQuake, Take Down, Hydro Pump, Muddy Water, all good moves. Earthquake can help your team be rid of pesky electric types such as Jolteon. Hydro Pump is for annoyances earthquake CANT handle. (such as Pidgeot for example) But shouldn't be used on ALL Flying types, like Dragonite or Salamance for example. For those two, your pretty much stuck and must use take down, but with the right attack stat, you can get some pretty hefty damage done to both of them. Muddy Water is more of a last resort move should you not want to use Hydro Pump or Take Down. Be it, its not very accurate, its slightly better than hydro pump, and handles Pokemon like Charizard easily. Swampert is a good Pokemon, but in PWO, its potential has yet to be reached.
Feraligatr has 4 main moves most people use. Super Power, (Fighting move) Ice Fang, Hydro Pump, and Crunch. Pretty wide variety of moves, and helps a lot too. Feraligatr can use Ice Fang to get some heavy damage done on Grass and Dragon types, and is pretty much its greatest move. Crunch is there to kill Psychic types like Alakazam, who stand in the way with good sp.def and speed, which all 3 other moves cant handle Alakazam. So Crunch is VERY useful if it can be used right. Super Power, not much to say. Kills pretty much any normal type. Snorlax, Sometimes Slaking, more as well. Pretty standard fighting move, and easily its most diverse. Hydro Pump is its most POWERFUL move, but sadly carries not much accuracy. But Hydro Pumps hit a lot and are a water types best bet. Feraligatr has reached its maximum potential in PWO, because its a great Pokemon.
Lapras... old classic if you may? This little one also suffers from low speed, but makes up for it with SKY HIGH HP and Defenses beyond comprehension. Added to that, its Special Attack is unbelievable! This guy has a lot of Potential in PWO, wouldn't you say. Confuse Ray, Ice Beam, Hydro Pump, and Body Slam is its best bet. Body Slam can paralyze things and actually is pretty good on a lapras. It makes Lapras all the more better in PVP and NPC battles. Ice Beam = Dragon and Grass Pokemons Death. Hydro Pump is for massive damage against bulky fire types in PWO (should there be any) and Confuse Ray is to annoy the hell outta your opponents. Overall, Lapras is a very useful water type, and be on the look out for any of them. You may just fall flat against them.
Starmie is an EXCEPTIONAL water type with amazing speed, high Sp.Atk, and just plain bad defenses. This Pokemon is offensive only, and heres a recommended moveset for it. Harden, Bubble Beam, Hydro Pump, and Confuse Ray. Set up with confuse ray first, and then harden away, because you can then take physical attacks easily. Best strategy you can use. Hydro Pump can OHKO mostly everything, and if not, Almost KO it. Even at type disadvantages, Hydro Pump is its best move to use. Bubble Beam is for that WEE bit of HP left that you dont wanna risk on Hydro Pump. Starmie is a good Pokemon in PWO, but it can be better if it had access to a wider pool of moves.