The Thetida Project and the Wreck of the Equa

By Fabio Ruberti, Photographs Marcello Di Francesco, 3D models by Dario Lupi.

19 January 2025—The first coordination meeting of the Thetida Project took place on June 29-30, 2023 in Vouliagmeni, Greece. This ambitious project, financed by the European Union’s Research and Innovation Programs for Cultural Heritage, aims to study and implement technologies and tools to improve the conservation of underwater and coastal cultural heritage to cope with climatic adversities, natural dangers, and pollution.

Project Thetida aims to achieve this goal through the development of preventive conservation technologies and strategies that include monitoring, preparedness, and risk management for underwater and coastal sites. The project seeks to identify and avert further threats as well as promote adaptation, reconstruction, and other strategies to restore normal conditions in the historic area. Long-term strategic approaches are also a part of the project scope.

This requires integrated assessments that consider the effects of multiple hazards on cultural heritage and their protection systems, as well as testing and evaluation of their effectiveness for a variety of pilot sites potentially threatened by such hazards.

A consortium of sixteen entities belonging to seven different nations will carry out the project. Of these sixteen entities, six are universities, two research institutes, one public body, three non-governmental organizations, and five small and medium-sized enterprises, of which one is IANTD S.r.l. (Italy). Four organizations are Italian, three Greek, three Cypriot, two Dutch, two Portuguese, one French, and one Norwegian.

The project selected seven pilot sites: three coastal and four underwater. Of the four underwater sites, one is located in Portugal (Algarve), one in Cyprus, and two in Italy. IANTD S.r.l. is responsible for the site of the wreck of the submarine chaser Equa of the Italian Republican Navy (RSI), sunk in 1944 after an accidental ramming near Cape Montenegro, just south of Riomaggiore (a small village near by La Spezia) about two miles off the coast.

The Program

The Thetida Project is a very complex program lasting 42 months; it is structured in Work Packages and each Package is divided into Tasks. The IANTD is mainly engaged in operational Packages and Tasks at sea on the Equa pilot site, which include making a 3D model of the wreck. Another task is to support the pilot site monitoring with instruments carried by Autonomous Underwater Vehicles (AUVs) produced by Edgelab S.r.l., another Italian SME belonging to the consortium and specializing in such highly technological vehicles . The project also includes a citizen science phase which also includesAUV-supported pilot site monitoring.

The operational protocol will be the one already widely tested by the twenty-year experience of IANTD Expeditions with the obvious modifications for this case. The first, obviously, is that the activities are part of an articulated and complex structure with a superior body; the other is that the activity, having a total duration of three and a half years, will be discontinuous and based on contingent operational needs. 

In these first two years of activity, IANTD achieved all the expected objectives. These mainly consisted of making a large part of the 3D model of the wreck and testing the Conductivity Depth Temperature (CDT) devices. CDT devices contain the sensors necessary for environmental surveys, with one unit worn by a diver and one unit placed on the wreck for a duration of three months.

The following members of the IANTD Expeditions participated in these activities: Cesare Balzi, Carla Binelli, Alessandro Brandetti, Massimiliano Canossa, Paolo Davide, Marcello Di Francesco, Dario Lupi, Lorenzo Rossi and myself. Furthermore, numerous divers participated in the underwater activities of the Thetida Project with citizen science tasks. 

A short film has been developed to document the activities carried out so far:

The Wreck of the EQUA

The pilot site is the wreck of a vessel sunk during the Second World War with a somewhat controversial history: the motorship Equa. She was built, together with sister ships Meta, Epomeo, and Sorrento, in the Tosi shipyards of Taranto in 1929, commissioned by the Società Anonima Partenopea di Navigazione of Naples and registered with the Maritime Compartment of Naples, for the connection with the islands of the Campanian Archipelago.

The name is a toponym that derives from the Latin “aequa,” which means equal or flat. The name also indicated the place where the town of Vico Equense stands today. Therefore, like her three sisters, her name indicates a location on the Sorrento Coas and the Island of Ischia (Epomeo)—all apt names as they are boats intended for local maritime traffic.

The Equa originated as  a passenger ship of 243 gross tons; small in size, she measured approximately 40 m/131 ft long and 7 m/23 ft wide with a hull measuring approximately 3 m/10 ft. It was built of steel and divided into 7 transversal, watertight bulkheads which guaranteed greater safety. The maximum speed was around 12 knots achieved by two 4-stroke diesel engines for 1200 horsepower.

Eleven years later, in 1940—again in the Tosi shipyards of Taranto—two more ships were built for the Società Anonima di Navigazione Eritrea: the Lago Zuai and the Lago Tana. These ships were supposed to carry out passenger service along the coasts of the Red Sea; however, when World War II broke out, they were requisitioned as auxiliary cruisers. As we will see later, the Equa will meet her fate with the Lago Zuai.

As World War II approached, the Equa was requisitioned by the Regia Marina (Italian Royal Navy) from May 13 to October 2, 1940 and assigned the initials F43 with port surveillance duties. After briefly returning to civil navigation, she was requisitioned again from March 11, 1941 to September 8, 1943 by the Regia Marina and included in the auxiliary fleet. In this second militarization, she was renamed AS105, transformed into a submarine chaser, and equipped with munitions: a 90 mm cannon, two 20 mm machine guns, and an anti-submarine system on the stern.

Following the armistice of September 8, 1943, the Equa was initially confiscated by the Kriegsmarine (German Navy), then sold and incorporated into the Republican Navy of the Italian Social Republic (an ally of Germany) as a submarine chaser stationed at Le Grazie—a small harbour village near by La Spezia—and attached to the Decima MAS. (Italian Navy Special Forces) Here, it fatefully collided with the Lago Zuai. 

Lago Zuai, too, was confiscated and militarized as an auxiliary cruiser by the Italian Regia Marina from 1940 to September 8, 1943. After the armistice, it was requisitioned by the Kriegsmarine, assigned to the 22 U-Jagdflottille in command of the Korvettenkapitän Friedrich Wunderlich, and reclassified as a destroyer with the acronym UJ 2220 (based in La Spezia).

Information related to Equa’s demise, due to an accidental collision with the UJ 2220 (ex-Lago Zuai) during a night anti-submarine patrol, is controversial. Official Italian sources indicate that the event occurred on the night of June 10, 1944, while the Germans claim it took place on the night of April 18, 1944. Both versions are corroborated by archival documents; so, at present, it is practically impossible to determine which date she truly sank.  The fact is that the Equa, obscured, while patrolling the La Spezia coast off the Cinque Terre in search of enemy shipping, was accidentally rammed by the German submarine chaser UJ2220—fortunately, the entire crew was rescued.

The only information on the incident is provided by German historian Manfred Krellenberg in his book “U-Boot-Jagd im Mittelmeer: Der Einsatz der 22. U-Jagdflottille” (Hunt for submarines in the Mediterranean: The deployment of the 22nd flotilla). He offers an account of the accident report in the Kriegsmarine documents: These specify that the two naval vessels, about two miles from the town of Riomaggiore, proceeded in darkness on a collision course. The UJ 2220 noticed the Equa when she was too close to attempt a disengagement manoeuvre. The very violent impact created a gash on the left of the Equa at the bridge level, which led to the rapid sinking of the ship. A German motorboat—which, fortunately, passed through the area—quickly intervened to save the castaways, and none of the sailors perished in the accident.

Where We Go From Here

Today, the wreck lies in a sailing position with an east-west orientation at a maximum depth of 40 m/131 ft with the deck at around 35 m/115 ft in an acceptable state of conservation. The bridge is still visible and, from it, you can access the lower deck full of debris and metal remains. On the outside, the hull is covered in encrustations and molluscs. On the bow, you can clearly observe the well-preserved cannon and the winch wrapped in a net; other nets hang on the edges of the wreck. From the command bridge, you can see the engine room. Continuing towards the stern, you pass by some very large windows that provide views of internal rooms. Finally, on the stern, there are still cables and equipment for anti-submarine hunting. 

The wreck is an oasis of submerged life; it is not uncommon to see conger eels, lobsters of decent size, and sometimes even sunfish wandering outside. Visibility is variable and can change several times even during the same dive. Currents raise the silt from the muddy seabed, creating dense clouds that greatly limit visibility, but which can disappear as quickly as they appear. This created considerable difficulties during the 3D modelling of the wreck.

The second plenary meeting of the members of the Thetida consortium was held from June 11-13, 2024 in La Spezia. During this meeting,  the team evaluated the results of the first year of research and planned the activities for the second operational season. Furthermore, future actions and research to be developed in the various pilot sites, including the Equa, include: 

1. Hyperspectral mapping of biophysical degradation of materials using methodologies and maps for detecting and monitoring corrosion of materials.
2. Complete 3D underwater representation of the site with optimization of experimental procedures and methodologies for the production of 3D representations.
3. Use of AUV platforms with installation of specific sensors such as multibeam/side scan sonar and data fusion with optical camera imaging and photogrammetric procedure.
4. Installation of smart buoy for autonomous and cost-effective energy harvesting with remote smart buoy access to provide the project with innovative in-situ environmental monitoring methods.
5. Underwater detection devices placed on the seabed and worn by divers.
6. Sampling and study on the deterioration of materials.

This is a very complex and ambitious research plan to be carried out over the next 18 months. The Thetida Project will certainly contribute to the preservation and protection of underwater sites and wrecks, and the Equa will complete its last mission.

FABIO RUBERTI was born in Pisa on 23 July 1955. Directeing his studies toward the exploration of historical wrecks, he obtained a master’s degree in history from the University of Pisa (Italy) with a thesis in underwater archaeology after studying the wreck of the World War I Austro-Hungarian battleship Szent István (Saint Stephen). Subsequently, he obtained his PhD with the University of Haifa (Israel) on the study of the wreck of the World War II Italian submarine Scirè. Entrepreneur,  diving instructor, researcher, expert explorer of wrecks, and fellow of the Explorers Club of New York, Fabio has dived and explored many of the most famous historical wrecks. He is the owner of the IANTD diving teaching agency for Italy, a pioneer of technical diving, and an author of numerous Italian-language diving manuals and several history books. He is also a renowned speaker in historical and diving conferences, journalist, and collaborator of numerous Italian and foreign underwater and historical magazines. In 2011, he received the Award of the International Academy of Underwater Sciences and Techniques; in 2021, he received the Golden Trident for lifetime achievement.