In Simple Terms
A team spent five days living underwater and went outside in diving gear to explore. The dark, cramped surroundings meant they had to stay close, communicate clearly, and work together. The experience offered useful practice for space travel, but it also showed that an underwater emergency can be real—not a drill that can simply be paused.
A Space Mission That Never Left Earth
Exploring the ocean floor may sound like a diving adventure. It becomes a much more serious test when a team is living in an underwater habitat and heading out on planned excursions without being able to return to the surface at a moment’s notice. That was the challenge for the SEA STAR crew during a spaceflight simulation: diving gear stood in for spacesuits, while trips outside the habitat became exercises in movement, exploration, and teamwork in a demanding environment.
SEA STAR is an analog mission, a type of experiment designed to recreate some of the conditions of crewed trips to the Moon or Mars without leaving Earth. These missions can test more than equipment. They can also reveal how crew members cope with isolation and difficult living conditions, organize their work, and communicate as everyday tasks become more complicated.
The mission commander, astrobiologist and explorer Michaela Musilova, had previously led about 40 analog missions simulating human journeys to the Moon and Mars. But SEA STAR brought a different kind of responsibility: living with the crew in an underwater habitat and leading them on excursions outside it. The habitat, known as Jules’ Undersea Lodge, was in Florida at a depth of 22 feet, or about 7 meters.
There is an important difference between an analog exercise and an actual space mission. A spacesuit equipped with life-support systems can weigh as much as 310 pounds, or 141 kilograms. By comparison, the analog suits used in many Earth-based training exercises typically weigh no more than 30 pounds, or about 14 kilograms. In many simulations, a trainee can also open their helmet and breathe the surrounding air if necessary. An astronaut in the vacuum of space cannot do that, and neither can a diver on an underwater mission.
Why Surfacing Is Not an Easy Option
The crew spent five planned days underwater in a state known as saturation. This occurs when someone remains under pressure long enough for their body tissues to absorb as much inert gas, such as nitrogen, as they can at a particular depth and pressure. As a result, an extended stay underwater is not like a short dive that can be ended immediately by swimming to the surface. Returning safely requires attention to the conditions of the dive and the proper safety procedures.
In ordinary diving, returning safely to the surface is the standard response if a diver becomes separated from the group and cannot find the others. That was not part of SEA STAR’s routine plan. The crew was committed to staying underwater for all five days, and an early return to the surface was an option only in an emergency. Under that constraint, planning and communication are not just signs of good organization; they are essential parts of managing risk.
Potential hazards included water leaking into diving equipment or the habitat, as well as health problems associated with high pressure underwater. Equipment failure or decompression sickness could also put a diver’s safety at risk. For that reason, the crew followed careful procedures before and during each excursion and treated the possibility of a malfunction seriously—much as a space crew must, since its members cannot simply take off their equipment and breathe the surrounding air.
Musilova’s concern did not stem from a lack of diving experience. She is a seasoned diver who has made dives in very dark ocean water and in caves. But leading the team changed what risk meant. Her responsibility was no longer limited to keeping herself safe; it extended to a crew living with her in the habitat and relying on her decisions. She was therefore more cautious and worried than usual, even when some parts of diving felt familiar.
Small Lights, Short Sightlines
SEA STAR’s equipment was not a replica of a spacesuit. The crew relied mainly on diving gear, with a few additions that made movement more like some aspects of working outside a spacecraft. The divers wore gloves and used handheld lights. The gloves protected their hands from sharp shells and other formations that could cause cuts, but they also made it harder to grip tools.
The effect was especially noticeable when the crew used cameras and suction equipment to clean up the underwater environment. Even a relatively simple task becomes harder when your fingers cannot move freely and you cannot handle objects with precision. That is an important lesson from analog training: protective equipment does more than shield its wearer. It can also change how work gets done, much as thick gloves limit astronauts’ ability to handle tools during a spacewalk.
The lights were essential because visibility at the site was extremely poor. Each beam illuminated only a short distance ahead—no more than a few feet—so divers could not take in the whole scene or keep an eye on teammates from far away. The crew moved side by side, using their lights to find their way and keep track of one another. With visibility so limited, staying close became a safety strategy, not merely a preferred way to explore.
Conditions like these show how a small area can still pose major challenges. When only a narrow slice of the surroundings is visible, a person must work out where they are from what they can see in the moment, while also keeping track of teammates and equipment. Losing focus or drifting away from the group could turn an exploratory outing into a situation requiring a quick response.
Communicating Before Contact Is Lost
Each excursion began with a plan, a discussion of alternatives, and a review of what to do in an emergency. Underwater, the crew used familiar diver hand signals and added some signals specific to the mission. This mattered because direct visual and verbal communication cannot be counted on at every moment, and the team needed to share information without relying entirely on communications equipment.
Agreed-upon signals are useful beyond the ocean. Analog missions on land can also face communications failures or conditions that make it difficult to exchange messages. If crew members already know how to make a clear request or give a warning with a signal, they have a practical backup that helps keep work coordinated. It is a reminder that simple procedures can be valuable—but only when the team has agreed on them in advance and uses them consistently.
Even careful planning cannot remove every fear of the unknown. Darkness, poor visibility, and the possibility of becoming separated can leave a diver worried about losing direction or being unable to find their teammates. During a five-day underwater mission, returning to the surface cannot be treated as a routine fix just because a crew member can no longer see the others. The mission’s rules remain in force unless an emergency calls for a change.
That is why backup plans and emergency drills are part of the mission itself, not just paperwork completed beforehand. The team needs to know what to do if communication fails, how to respond if members become separated, and what signs mean an activity should stop. A simulation cannot guarantee that every danger will be prevented, but it gives a crew a chance to test its response before future astronauts face conditions that leave no room for improvisation.
What Underwater Simulations Can Teach Future Astronauts
Working underwater does not make an exercise identical to a spacewalk. Each environment has its own hazards, and a dive simulation cannot replace spaceflight training. The value lies in a set of practical challenges the two settings share: wearing equipment that restricts movement, doing precise work with limited dexterity, following clear procedures, and coordinating with teammates in a confined or difficult-to-read environment.
Underwater excursions also provide a way to test human skills that cannot be reduced to equipment specifications. Team planning, awareness of other people, and decision-making with incomplete information all affect a mission’s safety. The commander’s role was especially demanding because she was not carrying out the task for herself alone. She had to keep an eye on her teammates and balance exploration with the discipline needed to protect the group.
Another clear lesson is that protective tools can introduce new difficulties. A glove reduces the risk of cuts but makes a camera and cleaning tool harder to use. A flashlight helps a diver see, but only within a limited range. Simply providing equipment is not enough: the crew must practice using it in the conditions they will face and learn how to work around its limitations.
Leadership also takes on a different character when a commander is responsible for people who depend on the whole team. Individual diving skill cannot replace looking out for others, nor does it remove the need to make sure the plan is being followed. The role demands extra caution, but it also gives crews a way to test how they manage people in difficult environments—a useful lesson for long journeys that require people to live and work together.
For Musilova, the demanding conditions did not erase the pleasure of exploring. Although the light revealed only a small patch of what lay ahead, she saw the unfamiliar terrain as an opportunity to develop her skills in orientation, navigation, and leadership. While keeping a close watch on her crew, she found that leaving the habitat made her feel more connected to the experience of an astronaut exploring the surroundings—driven by curiosity even as darkness hid most of the scene.
The Bottom Line
SEA STAR offered a tangible example of how an underwater setting can simulate some aspects of working outside a spacecraft, without suggesting that the ocean and space are the same. The crew spent five days in a submerged habitat at a depth of 22 feet, or 7 meters, dealing with poor visibility, equipment hazards, and pressure. Gloves, lights, hand signals, and advance planning were central to the work.
The mission shows that preparing for long, distant journeys takes more than an advanced suit. Equipment, the way people use it, and a crew’s ability to communicate and support one another all work together. A diving simulation cannot prepare astronauts for everything they may encounter, but it can expose weaknesses and sharpen teamwork before a mission reaches a point where a quick return or a request for help is impossible.