Sometimes called diving’s "best-kept secret" the western Pacific island of Guam has some of the most amazing diversity in the marine world. It is Micronesia’s largest island but is only 30 miles long and ten miles wide. But small things come in excellent packages as divers will find more than 400 coral species, 1000 fish species, 14 marine mammals and numerous invertebrates. This makes the island a treasure trove of undersea wonders.

Add to that World War I and II sunken ships, planes and other remnants plus deep drop-offs and amazingly clear and warm waters. Plus, on land, the island is easy to get to and well-equipped with many hotels and restaurants for any diver on most any budget.

The islands of Rota and Saipan in the Mariana Islands lie north of Guam and are also lush gems with much to see above and below the ocean.

New for 2019, this guide has it all and it was written by Lonely Planet author and Guam resident and internationally published photojournalist Tim Rock.

New photos and updated descriptions accompany approximate dive positions, maps, general location, most frequently dived depths, type of dive that can be expected, the dominant marine life and logistical requirements.