The Sky Shark first appeared in The Topper in 1968/9 followed by two further runs in 1971 and 1974. It was also a regular fixture in The Topper Book from 1969 - 1973.
The first story tells how Professor Jeremy Thatcher, inventor of the flying submarine The Sky Shark, is recruited by DIE, the Department of International Emergencies, along with his niece Jill and nephew John. Usually they find themselves up against CLAW, the Criminal League Against the World, but in this final story from the third series the mystery frogmen are... well that would be telling!
The Topper was published "every Thursday" (in reality it would have been in the shops the previous Wednesday to the cover date) so that's how I'm going to present it.
The artwork is by Keith Watson. Look out for a forthcoming post for more on him.