As you can well see when entering Adonis there is a lot of water. (If the scuba gear given you by Ergo didn't tip you off the giant lake might) It is really a pleasant looking place; and when I say pleasant I mean that hungry monsters will try to eat you and any family you bring along for a beach party.
The journey to Ergo. It starts (for those with Scheol Key) at the Halls of Scheol (Roch/Omni) or The Approach (Ocra/Clan). The road is full of Ironwood Girder monsters levels ranging from 100 to 120 (I did see one Robust Girder who was level 130) so its a good idea to pack a few med kits... or a high level friend.
At Necropolis you'll see Radiant Spirits, who are still generally below level 120 but they have a nasty DoT that can drain you of health and nano. There was two named ones, Jovial Spirit and Euphoric Spirit that dropped Novictum. Jovial dropped "Blueprint Pattern containing information about a Trapped Soul" which seems to be useless part of a quest that was never made.
So, a bit more fighting and you find Ergo, who is as talkative as ever. Just say you are in a hurry and rush through to get your ring and "Metawater Repellent Spiritech Suit" go to the portal and zone through.
There is a small bridge and another zone into what looks like a dungeon found all over Shadowlands. In here you find the standard monsters that will try to make you their lunch. Just fight straight through to another zone. (Looks like a pressure lock.)
Now you're underwater; be sure to have your 'Scuba gear' on or you may as well have zoned to reclaim. It's safest to run (slowly) to the west and then follow the wall north until you see a ramp on the east (aligned with the walkway you were on at the start). Running to that ramp will spawn a bunch of Slotherian which look like tentacles. (Most people die a few times at this point).
Note: If your lucky enough have an MP Anchor you at Ergo so if you die you can be warped back.
Once past the Slotherian's just head up the stairs and onto land with runspeed. Now your Scuba gear is a back item so for those professions that need a back item for AC you may have to swap it out. Just be sure to have your scuba on when zoning to a water area.