Okay, so a filler-y episode; I am used to how Chris Chibnall doesn't always set up the next episode with his plots, unlike Davies and Moffat.
[No ship Sherlock SPOILERS] I got a bit confused about what the Sea Devils were doing, but I liked the episode style (looked really 80s only with updated special effects) and the whole mcguffin involving the treasure.
Also, another highly questionable death instigated by the humans, like previously in the reboot with the Sycorax and recently Sontarans, AND Jon Pertwee's "Doctor Who and the Silurians".
What I really liked was how it furthered the relationship between the Doctor and Jas; I can't see it going anywhere, particularly with the reference to River Song (is she about to make surprise appearance?)
Also, Dan getting back in touch with his crush from earlier episodes was great; maybe she'll join as a companion.
It was great to see some old companions in the trailer, and I hope they will finally explain what was going on in those mysterious clips from before with Jo Martin's doctor - they have to stop tantalising us; I think she came between John Hurt and Christopher Ecclestone.