This may not be a book of the greatest 'depth' if you will excuse the pun, but what it does remarkably well is draw the reader into the subject by means of myriad short entries which have their own mini bibliographies. It is a smidgen under 500 pages in length, well designed and laid out and arranged under headings such as the names of vessels, places, techniques and technologies. At random therefore we find 'GIS' (Geographic Information Systems); 'Horse Ferry Wreck'; 'Lisht Timbers'; 'National Marine Sanctuaries' and 'USS Pilotfish' amongst the topics covered. Given that there appear to be between one and three subjects per page a guesstimate of the number of entries must be the better part of 500. There are also plenty of apposite illustrations, mainly small but both black and white and colour. A thematic table at the beginning gives some help in finding entries. The impressive list of contributors, and the 'advisory board' covers four pages.
The 'obvious' subjects seem pretty well covered - Mary Rose for example gets about two pages, four decent illustrations, though two of these are quite similar, and the mini bibliography lists three very familiar volumes, and two more specialist articles. Vasa gets a similar amount of space, with three pictures but six items in its bibliography. 'Mediterranean Sea' gets a little over six pages with five illustrations and about 30 bibliographic suggestions.The general standard of entries is good and well researched.
Any problems ? Only the usual ones with encyclopedias which are not multi volume monsters - and not totally exhaustive. I tried looking for 'Dreadnought' and 'Stratigraphy' (or lack of it with underwater sites): neither are there, though to be fair there is a section called 'Site Formation'. So nice volume: a joy to own, well produced, and now often avaliable as a cheap remainder - not perfect, but very good. Recommended, buy with confidence.