Unfortunately, the Under Da Sea achievement can't be completed with Azsharan Vessel because the sunken card is Cast When Drawn. I'm having quite a hard time with this achivement because most of the sunken cards are not in the meta decks anymore.
I got Should Have Gone for the Head using Rogue with Ambassador Faelin and Queen Azshara, lots of draw and Shadowstep. All you have to do is get Hydralodon from one of the two sources, play it, kill the heads once and then Shadowstep it and repeat. This will summon a total of 12 heads.
Unfortunately, the Under Da Sea achievement can't be completed with Azsharan Vessel because the sunken card is Cast When Drawn. I'm having quite a hard time with this achivement because most of the sunken cards are not in the meta decks anymore.
I got Should Have Gone for the Head using Rogue with Ambassador Faelin and Queen Azshara, lots of draw and Shadowstep. All you have to do is get Hydralodon from one of the two sources, play it, kill the heads once and then Shadowstep it and repeat. This will summon a total of 12 heads.