Shipwreck Diving on Gunboat C-58, Isla Mujeres
Updated: Sep 3
USS Harlequin (AM-365), named General Pedro Maria Anaya C-58, was intentionally sunk for diving and this huge artificial reef has become a favorite amongst the more experienced divers. Having evolved within its new underwater environment over the years, it is now an amazing deep dive site and one that, during the months of December to late March, is teeming with eagle rays that return annually to this area.
Located off the coast of Cancun, the shipwreck is just a 25-minute boat ride from Isla Mujeres. Two shipwrecks have been laid to rest on the seafloor, quite close to each other; Gunboat 58 and Gunboat 55.
These two wrecks were sunk by the Mexican government, creating artificial reefs to be used for diving, and have proven to be a top destination for divers visiting the area.
Diving these wrecks is not for the beginner nor the diver that has not dived in a while. There are year-round currents that are very strong and, sitting at 26 meters/ 85 feet, they are considered deep dives. These challenges make it an appealing dive for the more experienced divers amongst us and the currents are the reason for the return of the eagle rays to this area. The topography surrounding Gunboat 58 is beautiful white sand and an area that was previously devoid of anything of interest to the underwater visitor is now teeming with marine life.
The History of the Wrecks
Getting information on the shipwreck has proven to be a very difficult task with a lot of conflicting information. This is what I have gathered about her (Gunboat C-58) beginnings:
US Navy Career
USS Harlequin (AM-365) was an Admiral-class minesweeper built for the United States Navy where she served in the Atlantic during World War II
3 June 1944; Harlequin was launched by Willamette Iron and Steel Works, Portland, Oregon; sponsored by Mrs. Mary M Doig, whose husband and son were reported missing in action and who also had another son, a brother, and nine nephews in the Navy.
28 September 1945; She was commissioned with Lt. Henry R Darling, USNR, in command.
19 October 1945; She reported to San Pedro, California, for shakedown. Harlequin remained there until 29 November, when she sailed south, reaching New Orleans, Louisiana, on 15 December.
May 1946; She was decommissioned and placed in reserve. While she remained in reserve, Harlequin was reclassified as MSF-365 on 7 February 1955 but never reactivated.
1 May 1962; Harlequin was struck from the Navy list
2 Oct 1962; She was sold to Mexico
In 1962, after she was sold to the Mexican Navy, she was renamed ARM DM-20.
From 1976-1978 she was converted to an oceanographic research vessel and renamed ARM Oceanográfico (HO2) around the same time.
In 1993 she was renamed ARM General Pedro María Anaya (A08).
and this is where the information gets confusing
In the late 1990s, she was again renamed, this time to ARM Aldebaran (BE02), as a school ship. As of 2007, Aldebaran remained in active service with the Mexican navy.
Unfortunately, we know that Gunboat 58 was purposely sunk in the year 2000 to become our shipwreck dive site; so it is here where we have our discrepancy.
Sunk on May 28, 2000, Gunboat C-58 now lies in her final resting place at a depth of 26mt / 85 ft. However, Hurricane Wilma, in 2005, split the ship into two sections.
The stern, or the back half of the boat, has a descent line that leads to the larger part of the wreck and is ideal for penetration for those with the proper certification. The stern is very open and large schools of fish live inside. Several rooms can be explored, making it ideal for the wreck specialty and there is even a bathroom with toilets if you know where to look.
For those doing their wreck specialties, the stern has very large openings cut into the sides so that very easy entry and exits can be made with very little deviation from vertical distance to the surface. There are other more restricted passages that are ideal for exploring while practicing your reel techniques.
The bow, or the front part of the boat, lies down current approximately 100 meters/ 300 feet away or an easy 5-10 minutes diving (depending upon the current). This smaller part of the boat can be appreciated resting on its left side with little penetration. Very few people visit this part of the shipwreck so it can be a nice drift to end your dive if your air consumption allows. Well worth the visit and great for seeing Spotted Eagle Rays.
Length 184’6’’ / 56.23meters
Speed 14.8 kts
Armament: One 3’’/50 dual purpose gun mount, two twin 40mm gun mounts, six 20mm gun mounts, one depth charge projector (hedgehog), four depth charge projectors (k-guns), and two depth charge tracks
Propulsion: Two 1,1710shp Busch Sulzer 539 diesel engines, Farrel Birmingham single reduction gear, two shafts
Eagle Ray Season
The diving at the wreck is amazing all year round but during the months from December through to March, migrating eagle rays can be seen here in large numbers and the area becomes a virtual "fly-zone".
During the peak of the Spotted Eagle Ray season, you can see 50-100 of these amazing creatures gliding effortlessly above the wrecks. They patrol enormous territories in search of food, mates, and amusement. The strong currents that surround the shipwrecks are what attract the rays and schools of them are seen swimming serenely close above your heads or frolicking in the water.
With wingtips that can span 3 meters/ 10 feet, they are part of the Myliobatidae branch of rays which are known to swim in the open ocean rather than close to the seafloor. Despite having poisonous stingers they are also known to be shy and non-threatening when in large schools. A spotted eagle ray will glide by or provide the pleasure of being watched as they penetrate the sandy bottom looking for their favorite food: concha
One of the beautiful things about artificial reefs is watching the changes over time that the ocean causes and the amount of marine life they attract. The Gunboat C-58 is no exception.
The shipwreck is now covered in Corals and Sponges and large clams can be seen on the sides of the ship if you are lucky enough to spot them before they close up.
Inside the stern are large schools of Grunts and Jacks and huge Green Moray Eels make their home there too. During turtle mating season we see the majestic Loggerhead Turtles passing by for a visit and Nurse Sharks can often be seen hiding away under the hull of the wreck. Besides all of these, you will see Barracuda, Lobster, Grouper, Hogfish, Lionfish (unfortunately), Parrotfish, and much much more. Every dive is different.
This dive is an advanced dive and should be treated as such. The very strong currents and depth mean that a diver must have experience before attempting this dive. A very strict screening process applies to be able to participate in this dive for the safety of both the diver and the guide.
The shipwreck once had lines by which boats could tie but unfortunately, many large vessels were responsible for ripping the identifying buoys off the shipwrecks by tying up to them. Now the entry to the shipwrecks is by a coordinated backward roll, negative entry. An underwater swim can take you to the descent line or directly to the bottom. This means that divers must be confident in their ears and diving skills.
The ability to listen to your guide and follow their advice will mean a fun dive for all. Safety and coordination with your team are paramount to the enjoyment of this dive. Because the dive is in the open ocean, surfacing in a controlled manner with the use of a DSMB is important as is a safety stop at the end of the dive.
26 meters / 85 feet
Required Experience Level
Advanced Open Water Certified Diver / Experienced Diver
Average Underwater Visibility
20 meters / 65 feet
Average Water Temp
26 Cº / 79 F°
Normal Dive Time
25-30 minutes (safety stop required)
USS Harlequin (AM-365). (2022). Wikipedia. https://en.wikipedia.org/wiki/USS_Harlequin_(AM-365)