Fathom Dweller

Head to the Broken Shore and find Drak'thul at 37.19, 71.65. Talk to him repeatedly until he has nothing more to say and tells you to go away — exhaust all dialogue options before moving on.

Travel to the cave at 58.5, 54 on the Broken Shore — look for the green torch outside the entrance. Inside, find the Mound of Dirt at the back of the cave and loot the Weathered Relic from it. If rocks are blocking the cave entrance, relog to clear them.

Go back to Drak'thul at 37.19, 71.65 on the Broken Shore and talk to him repeatedly again until he has absolutely nothing left to say. You will notice a red orb on his table and small rocks that mark the locations of the remaining orbs across the Broken Isles.

Find and click all 10 Hungering Orbs in strict order from Orb 1 to Orb 10 — the sequence will not work otherwise. Orb 1 is accessed via the cave entrance in Azsuna at 37.95, 37.43. Orb 2 is reached via the cave entrance in Val'sharah at 32.86, 75.77, with a path starting at 63.06, 35.53 in Suramar. Orb 3 is in a cave in Highmountain at 41.5, 81.16. Orb 4 is in a cave on the Broken Shore at 29.27, 78.37. Orb 5 is in a cave in Azsuna at 59.33, 13.09. Orb 6 is found in Stormheim at 67.3, 14.77, located under the neutral Toothless Great White shark. Orb 7 is in a cave in Val'sharah at 55.84, 38.4 — the orb is under the skull. Orb 8 is in a cave in Azsuna at 54.02, 26.21 — the orb is next to a pillar under a fern. If an orb cannot be clicked, it may be on cooldown — try switching to a different realm shard.

Once all 10 orbs are activated, locate and defeat Kosumoth the Hungering, which spawns as a world quest in Azsuna.

After killing Kosumoth the Hungering, check the Kosumoth world quest reward regularly — the Fathom Dweller is a possible reward from this world quest and grants 108% swim speed compared to the base 67% swim speed without it.