National Park Service
War in the Pacific, Asan BeachView of Invasion Beach Deck of the CormoranLVTSherman Tank

Diving in War in the Pacific National Historical Park

Palm lined coast Palm lined coast

Guam, the most strategically important U.S. possession in the Pacific, played a dramatic role in the early moments of America's involvement in both World Wars. In 1917, the skipper of the German raider SMS Cormoran scuttled the ship in Apra Harbor the day the U.S. entered the war rather than see it fall into enemy hands.

In 1941, Japanese planes attacked the island within hours of the raid on Pearl Harbor. Guam surrendered two days later becoming the first U.S. territory to be occupied by Japan. The eventual reinvasion of Guam in 1944 by American amphibious forces is the primary focus of the park. The invasion beaches at Asan and Agat are managed by the Park Service; they comprise a prime diving environment with warm, clear waters, gently sloping bottom, and a vibrant benthic community.

Large pelagic fish often visit from the deep waters that surround the island. In fact, water doesn't get any deeper on this planet than the nearby Marianas trench with its almost seven-mile-deep abyss.

In addition to the natural attractions of Guam underwater, the plentiful residues of warfare, including the ships in Apra Harbor and the detritus from the 1944 reinvasion, are sprinkled throughout park waters. An amphibious vehicle at Gaan Point escaped postwar clean-up efforts as did many projectiles and bombs.

The U.S. Navy and the government of Guam manage Apra Harbor, but the National Park Service has played an active role in surveying the harbor's shipwrecks and in helping to develop educational packets for diving tourists. Though not in the park boundaries, the shipwreck dives in Apra Harbor will be covered in this guide. It is one of war's ironies that the majority of visitors to Guam's vestiges of World War II, on land or under water, are Japanese. Park brochures are printed in Japanese as well as English, and many of the dive charters cater mainly to Japanese tourists.


Location: Guam, western Pacific
Skill level: Beginner-intermediate
Access: Boat or shore
Dive support: Agana
Best time of year: May-October
Visibility: Good to excellent
Highlights: War materials, reef
Concerns: Avoid touching ordinance, can be unstable.
Rules and Regulations

Dive Overview

Getting to Guam is easy. Easy, that is, once you have made a commitment to travel to the Western Pacific. Air Micronesia flies there daily from Honolulu and travelers to Japan, the Philipines, or Australia find it and easy stopover or side trip. Guam is also the logical jumping off point for trips to Palau (now Belau) or Truk(now Chuuk), two other diving meccas. A certified diver visiting Guam for any reason, business or pleasure, would be foolish not to spend a little extra time diving.

Diving logistics in Guam are also easy, with many dive shops, group outings, and charters to pick from. You can dive from shore right behind the visitor center, but boats or inflatables open more territory for exploration. Water temperature and air temperature both hover at an average 80 degrees F. The rainy season is May to November. That is also some of the best time to dive.

Unless you are planning very long diving days, wetsuits are unnecessary. Lycra skins are recommended for protection from the sun more than from the chill of the water.

The territory of Guam's Department of Parks and Recreation has jurisdiction over many underwater areas in Guam and has worked with the NPS and the U.S. Navy on regulating diving activities in the Territory. It would be useful to check with these folks regarding any information brochures or special rules that may exist for diving in Guam.

Be aware that discarded munitions can still be found in the park. A well-known concentration is near Camel Rock. Besides the usual admonitions against touching this material, we point out a special concern: Some of the ordnance has broken open, displaying phosphorous components. Think back to high school chemistry and recall what phosphorous does when it is exposed to air-and be extremely cautious.


Dive Sites


Hap's Reef is one of the best reef dives in the park. It is located in the Agat Unit of the park, northwest of Ga'an Point. The depths range from 25 to 60 feet and the reef is home to a large of population of very tame tropical fish-tame because they have been hand-fed by divers. There is a lot of nicely developed coral reef even though in years gone by this area was damaged by dynamite fishermen.


This is a patch reef-a reef that emerges in patches from the sand-and with a lot of free swimming pelagics and a variety of tang, clownfish, and other reef-dwellers. The clear water is well suited for general exploration. It is easiest to get here by boat, but take care to drop your anchor in the sandy areas, not on the coral.

Ga' an Point/Amtrac is an interesting area to browse because of the proliferation of coral and the myriad tiny creatures that make their homes on the coral heads and in the surge channels between them. Of historic interest is the amphibious tracked vehicle left here from the invasion. It lies in 50 feet of water and is located by swimming west on a compass course from the end of the jetty. A nearby sewer outfall has made this place problematic for diving on some days. If it’s one of those days, you’ll know.


Between Asan Point and Adelup Point is the Asan unit of War in the Pacific National Historical Park. The visitor center is located here on the beach off Marine Drive. The novice may want to snorkel the shallows behind the visitor center after seeing the displays and checking with rangers inside. Outer reaches of this unit are deeper and scuba divers will want to visit them from boats.


The sites in Apra Harbor are not in the park, but the NPS has actively helped its navy and territorial partners in management and preservation of the sites.


This is probably the most popular wreck diving site on Guam, and no wonder. Imagine the largely intact remains of a German raider (Cormoran) scuttled in 1917 on the day of America's entry into the "war to end all wars." Then, as if a study in irony was planned, the World War II Japanese armed transport Takai Maru joined her on the bottom in 1943. The ships lie in 130 feet of water and to see them both thoroughly takes at least two dives. The upper works of the Tokai and portions of the Cormoran can be seen on one dive less than 100 feet in depth. However, you should be on at least a 120-foot decompression schedule if you explore Cormoran more thoroughly.


Another excellent wreck dive, the Kitsugawa is not far from the Cormoran/Tokai. It lies in 140 feet of water and is sheltered in the harbor like the others. A Japanese transport, it was sunk by a combination of U.S. submarine and torpedo plane attacks during the war.


Though not well known or featured as a dive site, there is a wreck-the Aratama Maru-in Talofofo Bay on the southeast shore of Guam that is worth a visit by the wreck enthusiast. Visibility is poor here (at least for Guam). Don’t expect to see more than 15 to 20 feet.




Diver-down flag must be displayed while divers are in the water.
Removal of artifacts is prohibited

Last Updated: October 30, 2012