The short answer is: as a beginner, it doesn't really matter. You should focus on finding the right instructor for you, not the federation.
Beginner students
As mentioned above, as a beginner the only thing that should matter to you is to find a good instructor, someone with whom you will feel at ease and who will make you feel safe in the water. If you're not fluent in English, you might also want to go for an instructor who speaks your own language.
Now should you take the athletic performance of an instructor into consideration when you start your journey with freediving? Probably not. A level 1 instructor who has a flair to convey his/her passion and works mostly with beginners can sometimes be as good, if not better for you than someone who would have broken the 100m mark and might be better at coaching athletes. Ideally, you will want to learn with an instructor who can put him/herself in your shoes, and guide you accordingly. You don't need a record holder.
Here's Umberto Pelizzari's take on the question as he explained it in The Freedive Café podcast in 2018.
Intermediate-level Students
If you found a great instructor as your beginner's course instructor and are happy with the course material, you can continue and move up to the next level with the same person and federation. Going from one federation to another is usually easy, but with some federations, you might have to demonstrate your skills or do a cross-over (cf. paragraph below).
Master-level Students
Our platform is designed to make it easier for (very) advanced and/or competitive freedivers who are also instructors, and for students who wish to find a high-level coach to do that as well.
If you're looking for someone particularly good at a specific discipline or even for an athlete that would be among the very best in the world, you will be able to find what you want through the filters on our website.
Edit: please note that instructors have the ability to freely edit their own performance bests (PBs). We verify every document that could have an impact on the students' safety, i.e. professional accreditations, emergency first responder (EFR) / cardiopulmonary resuscitation (CPR) certifications as well as professional liability insurance policies, but not the PBs. The freediving community is relatively small though, especially at a certain level of performance. Most freedivers would never consider lying on their performance, and course listings are visible for all to see so it is safe to say that the listed PBs will reflect the freediver's actual performances.
Federations
We have put together a list of the different federations which courses are available through our platform. We would encourage you to browse through their websites to get a feel for yourself regarding their respective approach to freediving. We have also added a short description for some of these federations which we've known well and for a long time. Doing so, we've tried to remain as unbiased as possible, the aim being to advise all of you in the best way possible.
Edit: if you're an instructor or a representative of one of the listed federations, please feel free to get in touch, should you think your federation is not represented in an accurate light. Please do the same if you want to provide us with a description containing an "insider touch" for the federations which only have a short description at the moment.
Having a very good reputation, we made it possible for instructors of the FII and PFI federations to offer their courses through our marketplace, but as we have no specific knowledge about those federations that would add value to the reader, so we just gave you the link to their website.
Widely considered as the reference of freediving, you can hardly go wrong with an AIDA instructor. This non-profit organization is run by passionate freedivers (athletes, instructors, medical practitioners), the course material is thorough and well taught and will have you go through almost every aspect of the sport. Aside from education, AIDA also sets the standards for safety and international competitions.
AIDA International also tries to constantly innovate and recently started a "Youth Program", specifically designed for kids. AIDA has created its own "Freediving Emergency Medical Responder" course and is working with the very best practitioners in the field. This course is probably the best first aid/CPR course you can find as a freediver, as it is specific to freediving and not a generic first responder training.
At a professional level, instructors can easily open their freediving center or work as freelancers, given the brand recognition and the accessible cost structure of the certification fees (50€ a year for the membership, and 10€ per AIDA 1 certification, 20€ starting at AIDA 2).
Also, since AIDA is structured as a non-profit organization, you know that the certification fees will be put to good use for the development of the sport.
This federation was developed by the pioneer of the sport, Umberto Pelizzari. Their educational system is described as enabling "everyone to approach freediving in an aware, safe, and fun way."
They have instructors all over the world but are most active in Europe. For more information, you can listen to Umberto Pelizzari in these two episodes of the Freedive Café.
Apnea Total was developed by freediving lovers, in an approach focusing on the student experience in and out of the water. With their courses, you're likely to go through a discovery journey, instead of course chapters and requirements*. Those who want more out of their experience than just a standards-based freediving course will probably find what they're looking for here. They also have an easy-going and environmentally friendly culture and try to facilitate initiatives to protect the environment. AT instructors can either work independently or open their own centers. The cost structure of the certification fees for instructors is simple and among the lowest on the market for professionals so their courses are also usually more affordable than other federations courses.
*As a student you can climb the ladder of their courses more freely than with some other federations, however, you might not be able to use your AT certification to directly access other federations' higher-level courses without demonstrating your skills first, or doing a cross-over.
The World Confederation of Underwater Activities was initially established in 1959 and regroups today 130 national federations over all continents. In addition to organizing international underwater sport events, it is at the forefront of technical and scientific research and development. Today, CMAS is recognized as the official international federation for freediving by the International Olympic Committee, which is why world championships are usually organized in parallel, both by AIDA and CMAS.
CMAS offers a very serious and thorough course program for recreational freediving, and their centers can be found all over the world, although they are often associated with pool-related disciplines.
The up and coming federation. Using quite in-depth education material, and geared toward performance and competition, this is where you will find the biggest community of active freedivers (online and through their "deep weeks"). We recommend this federation to you if you want to really work on improving your performance while having fun in the process.
The educational system itself was created by Natalia Molchanova, the uncontested greatest freediver of all time, and has since then benefited from the expertise of world-class freedivers, among which her son Alexey, the current world champion in Constant Weight (CWT) and Free Immersion (FIM) disciplines. They regularly update the educational material with the latest developments and discoveries in the sector.
Their certification cost structure is accessible and interesting for instructors, which can also make their courses more friendly for the student's finances.
Additionally, once they complete a course, students can enlist to "Base Training", a very well designed and constantly updated training program for anyone who desires to improve and develop their skills further.
PADI is amongst the most sought-after scuba diving federations, and if you're already a PADI diver, you'll have an easy time accommodating.
Their educational material is well structured and easy to follow with the PADI Freediver™ course, an e-learning curriculum accessible online and through an app.
You will have no problem finding a PADI freediving center or instructor wherever you go.
The downside is that as the certification fees are slightly more expensive than with non-commercial federations, you will likely pay a bit more.
RAID is similar to SSI (↓). They offer affordable prices and slightly lower requirements to go through the levels of education.
Similar to AIDA in terms of material content and requirements to go through the first levels of education. On the plus side, you'll get access to really well designed and reader-friendly educational material through the MySSI app. Which you will also be able to read/watch on your phone or tablet. If you're already an SSI scuba diver, you'll also be in a familiar environment, and will be able to add certification cards to your diver's profile.
Some of the best freedivers in the world opened up their own center with SSI, so you might well end up training among some of them. SSI is also quite good at marketing and will be there for you if you want to turn your passion into a business, provided you open your own center (all their instructors have to be working with an SSI school, and cannot work as independent instructors).
The downside of SSI for the student is that the course material and certification fees are higher than with most other federations, so you'll likely pay a bit more.