Shipwreck Diving on Gunboat C-58, Isla Mujeres

USS Harlequin (AM-365), named General Pedro Maria Anaya C-58, was intentionally sunk for diving, and this huge artificial reef has become a favourite amongst the more experienced divers. Having evolved within its new underwater environment over the years, it is now an incredible deep dive site that, from 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 wrecks 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 neither for the beginner nor the diver who 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 a place previously devoid of anything of interest to the underwater visitor is now teeming with marine life.

The History of the Wrecks

Obtaining information about the shipwreck has proven challenging, with a significant amount 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 and served in the Atlantic during World War II.

• 3 June 1944: Harlequin was launched by Willamette Iron and Steel Works in Portland, Oregon. She was sponsored by Mrs. Mary M. Doig, whose husband and son were reported missing in action, and who had another son, a brother, and nine nephews serving in the Navy.

• 28 September 1945: She was commissioned with Lt. Henry R. Darling, USNR, in command.

• 19 October 1945: Harlequin reported to San Pedro, California, for shakedown training.

• 29 November 1945: She departed San Pedro and arrived in New Orleans, Louisiana, on 15 December 1945.

• May 1946: She was decommissioned and placed into reserve.

• 7 February 1955: Reclassified as MSF-365 while in reserve but never reactivated.

• 1 May 1962: Struck from the Navy list.

• 2 October 1962: Sold to the Mexican Navy.

Mexico

In 1962, the ship was sold to the Mexican Navy and renamed ARM DM-20.

Between 1976 and 1978, she was reportedly converted into an oceanographic research vessel and renamed ARM Oceanográfico (HO2) around the same time.

⚓ Note: This is where the history becomes confusing.

There is some confusion in public records, suggesting that by 1993, with some records indicating that she was renamed again as ARM General Pedro María Anaya (A08). Later in the 90s, she supposedly became ARM Aldebaran (BE02) and served as a school ship into the 2000s. However, based on verified dive records, INAPESCA archives, and firsthand accounts from local diving history, we know that the C-58 wreck off Isla Mujeres was already sunk intentionally as an artificial reef by 1980.

The renaming timeline appears to apply to sister ships of a similar class, not the C-58 itself. The C-58 divers' visit today was underwater well before the 2000s and was further broken into two dramatic sections by Hurricane Wilma in 2005.

Present Day

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 huge openings cut into the sides so that easy entry and exits can be made with little deviation from vertical distance to the surface. Other more restricted passages are ideal for exploring while practising 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.

Specifications

• Displacement 945lt

• Length 184’6’’ / 56.23meters

• Beam 33'

• Draft 9’9’’

• Speed 14.8 kt

• Complement 104

• 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 fantastic all year round, but 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 surrounding the shipwrecks attract the rays, and schools of them are seen swimming serenely close above your head or frolicking in the water.

With wingtips that can span 3 meters/ 10 feet, they are part of the Myliobatidae branch of rays 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 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 its favourite food: concha.

Marine Life

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.

photo @jaspersblueworld

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.

Large schools of Grunts and Jacks are inside the stern, 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 wreck's hull. Besides all of these, you will see Barracuda, Lobster, Grouper, Hogfish, Lionfish (unfortunately), Parrotfish, and much more. Every dive is different.

The Dive

This dive is an advanced dive and should be treated as such. The 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 wrecks by tying them 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 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 using a DSMB is essential, as is a safety stop at the end of the dive.

Depth

26 meters / 85 feet

Boat Ride

25 min

Dive Type

Deep

Drift - Frequent Strong Currents

Artificial Reef - Wreck

Experience Level 

Advanced, Experienced Diver

Recent diving experience

Average Visibility Underwater 

20 meters / 65 feet

Average Water Temp

26 C°/ 79 F°

Dive Time

25-30 minutes (safety stop required)

To view the fish surveyed here with reef.org, click HERE.

DM Mapping project - Lindsay Burns and Emmanuel Rojas

USS Harlequin (AM-365). (2022). Wikipedia. https://en.wikipedia.org/wiki/USS_Harlequin_(AM-365)