I dunno about seadra but whiscash is actually pretty hot, pair it with a grass type and u can beat electrics, it can check birds, great answer to fire types (beware HP grass though), good pupitar check, and decent movepool [surf, ice beam, spark, earthquake, hidden power, rock slide, toxic, protect, rest, sleep talk make up most of its movesets]. Like Wailord it's a little unpredictable at first glance, due to having the capacity to go mixed, physical, special, and more offensive or defensive, albeit without curse or explosion it's much less immediately threatening. It is really incredibly bulky; I tend to prefer a bulky tank/pivot set with ice beam, earthquake, protect, surf/toxic. Surf if the team's pretty pupitar/sudowoodo/graveler weak, toxic otherwise. I mean I can go more into why I prefer it, and the EVs, but damn it's just effective at answering lots of stuff, whilst it can be bait-killed since it covers so much you generally do add redundancy alongside it making that less problematic [e.g. whiscash+cacturne handles all electrics if you play carefully, even haunter too unless giga drain+hp fire..; whiscash+pelipper answers all fire types really handily as well as doing a multitude of other things].