This podcast starts with its own prequel - Fathom. Derelict is currently available via the premium subscription and I haven't listened to that yet. But Fathom is an absolute masterpiece. I was at the edge of my seat all of the time. It's very well written and the voice cast is excellent. I especially like the role of Agent Blayne, played by Michael Mau.
The setpiece - an underwater base near an ancient artifact - is very claustrophobic and gave me "The Thing" vibes at times. It's really hard to pull off a story and audio design so well that you can feel immersed for hours - but this audiodrama really did it for me.