I'll elaborate: The Specially Defensive set puts more emphasis on recovery than the physically defensive set, since the specially defensive Jellicent will take more damage from physical moves than before, and it might not have time to use Recover to heal itself. The Choice Specs set forgoes recovery completely in favor for hitting the opponent hard. Water Spout also gets weaker the lower Jellicent's HP gets, so switching in to a predicted Water move is very useful to help get Water Spout back to full power, or at least close to it.
Ok, Id been working on this Sassy Jellicent with 252 Hp; 150 Sp Def and the rest Sp atk. With Surf, Ice beam Toxic and shadow ball. Kind looks like a wreck typing it out lol