The plan for the fourth expedition within the Mahafaly Karst Exploration Projects, aimed at exploring the karst area in southeastern Madagascar, included two main objectives: underwater filming for a documentary in the Aven cave and delving into the unexplored areas of Ananjamba.

The main problem during the previous expedition was access to gases and fuel for the compressors, so this time the team decided to focus largely on diving with CCR rebreathers, treating open circuit sidemount diving only as a supplement.

The goal was theoretically simple: to maximally extend the length of the discovered corridors, already equipped with guide lines over three kilometers.

However, to understand the scale of the challenge, one must know that Ananjamba has only one entrance, and reaching new parts requires passing through the entire section already discovered. This means several hours of diving and passing through many tight restrictions just to get to the place where the exploration of the next section can begin. The return is via the same route, meaning additional hours spent in the water.

Utilizing all the capabilities of the Megalodon CCR rebreather, Patrick Widmann successfully added several hundred meters to the already discovered parts, in line with the earlier predictions of Ryan Dart and Philip Lehman, who first explored the corridors of Ananjamba a year earlier.

The dives into the remote parts of the cave led to the discovery of huge corridors adorned with complex rock formations, which surpassed in their spectacularity everything the team members had seen so far in Madagascar.

In parallel with Patrick's dives, Phillip and Ryan conducted methodical searches of parts that were still within the reach of the sidemount open circuit configuration. This led to the discovery of many new corridors, some of which ended in blind alleys, but several suggested significant exploratory potential.

However, diving in the more distant parts of the cave brought a new problem: some of the restrictions proved too tight for a diver with a CCR rebreather in a back-mount configuration. This suggested the need to use sidemount CCR rebreathers and simultaneously meant a change in exploration strategy.

The expedition was a complete success. At its conclusion, the total length of the discovered corridors of Ananjamba was 7.3 kilometers, more than the previously explored Malazamanga cave, confirming its status as the longest submerged cave in Madagascar. Interestingly, the cave still has great exploratory potential, positioning it as a contender for the longest submerged cave in all of Africa.