Mid twentieth-century books on the sea, set of four iconic titles in matching hard covers

Four iconic mid-century 1950s-1960s hardcover books on seafaring and ocean exploration.
Titles:
The Silent World by J.Y. Cousteau
The Kon-Tiki Expedition by Thor Heyerdahl
Sailing Alone Around The World by Joshua Slocum
Of Whales And Men by R.B. Robertson
The books are in good condition although all have some spotting to the pages, particularly at the edges, as you can see in the photos.
The books variously feature maps, illustrations and colour plates.