In about 1978 I read a book on holidays and cannot remember the name and have been searching for years. Maybe someone here can help.
The story was of two pilots who crashed on a sandbar in the English channel which began to subside until they were pulled under and into an underground world with cities and people etc. They helped out with a conflict between the subterranean dwellers which involved water supplies and they built a rudimentary airplane.
That is about all I can remember aside from the fact that i really enjoyed it and would love to read it again. Thanks in advance for any help.
