Throne of Tides
Big thanks to Gilthresa for putting these together, and allowing me along for the ride!
Throne of the Tides
This achievement is obtained by killing one of the adds that spawn with the bosses geyser ability, to do this simply kill two of the three adds that spawn and get the last add to about 50k health, get your whole group to stack near each other so you know where the geyser will spawn, then kite the add on to the geyser before it goes off.
Prince of Tides
When the Unyielding Behemoth spawns you will need to keep it alive and have no one DPS it, simply keep it alive till phase 2 and it will die automatically and you will get the achievement. This does require a decent amount of extra healing, so help your healer out by not standing in the black clouds.