User blog comment:Wolfba3103/Lost River?/@comment-32654153-20181227030612/@comment-37948736-20181228224252

there are other entrances though. I found two, one in Blood Kelp Trench, which is the one i think your talkinga about, and the other directly benath the floating island is a Deep Grand Reef which has an entrance too. Also, idk about building a thermal plant for that, i got the message before i even had aerogel.