Aw Dewgong. One of my favorite Pokemon. Back when I was six, my bus driver loved to play Pokemon. She traded me 4 of her level 40 Pokemon when I needed them most for just some caught Pidgeys. Howeer, she would never trade hr favorite Pokemon, her Dewgong. Well, enough of the story-telling, here is my Res-talk Dewgong, which has the ability Thick Fat and is EV trained in HP and Attack:
Rest: Heals Dewgong fully and is hated by most everyone who has to face Dewgong users such as Lorelli.
Sleep Talk: A must with Rest. This is not that popular a choice among all Dewgong users because of Hydration, however, mine has the ability Thick Fat.
Aqua Tail: Good power, decent accuracy, STAB, deals with Rock types.
Ice SHard: High accuracy, STAB, priority, deals with Grass types.