This is a great addition to the Companion Chronicles range by Big Finish!
Starring Frazer Hines and Anneke Wills, both actors give extremely credible performances of not only their own characters but also of Ben and the Doctor. Hines' portrayal of the Doctor is nothing short of magnificent, he really does capture the mannerisms and the characterisation of Patrick Troughton as the Doctor, and it makes not only this story but every companion chronicle he does even more engrossing!
The story/plot isn't exactly difficult to follow in this release, but then that's what I like about the TV stories from this era; there's an innocence and simplicity about them! The Selachians are good villians that I have enjoyed in print before, but this is my first time of hearing them on audio (I believe they have been used in a Big Finish story before) and to be honest I didn't really like sound design for their voices, but it's got to be hard to come up with something that sounds like a talking shark in a spacesuit!
Overall, a really listenable and enjoyable Second Doctor story made by Frazer Hines' and Anneke Wills' strong performances, and one I'd recommend!