So we were both in Euronat and for a day-trip to CHM Montalivet.
Here are some tips:)
We flew to France, so we needed to get to the campsite by public transport. From Bordeaux main railway station there's a bus running a few times a day to Lesparre (Transgironde line 703). From there there are even less busses that go to Montalivet (712), stopping both at CHM Montalivet and also later at Euronat. In total it took about 3 hours from Bordeaux to Euronat (120 km), but it was very cheap, it's about 3 EUR for the whole trip.
In Euronat you can rent small holiday houses (mobile homes) for a week, it was quite reasonable price as we were 6 of us. You have to pay extra if you don't bring your own bedsheets or towels.
The entire campsite is in a huge forest, the houses have some garden, terrasse with sunbeds, table and chairs. It really looks like a huge village but the houses are quite far from each other, so it still feels like being in a forest. Because it is so big area, you also don't feel that there are so many people. It feels nice calm everywhere.
The beach from the entrance is quite a distance away, so it's quite handy to have a bicycle. You can rent also a bike for a week (36 EUR). Lot of people ride the bike, also to get to the "centre" where there are many shops (also supermarket), bakery, restaurants and a stage where in the evenings there was some live music, and also sport fields and rooms for activities/animation. The archery is further away, it was quite nice acitivity even for beginners!
Altough there were signs reminding the people that "you are in a naturist camping - go naked", I had the feeling that less than 50% did so. On the beach it was better ratio, but even on the beach there were about 10% clothed people, the lifeguards/security didn't remind them about it.
The beach is very nice, sandy and very wide, with nice waves. It can be also dangerous so i'ts only allowed to go into the water where there are the lifegueards (marked with flags).
From Euronat there is a nice bike road to the city of Montalivet (there's also an ALDI supermarket, open also on Sundays) and further to the campsite CHM Montalivet. It was about 30 min by bike to Aldi, and 45 min to CHM. With the Euronat-badge you we could get free day-pass to the CHM campsite at its reception. The sport fields are near to the entrance, there we still didn't feel that it's a naturist campsite, only more inside the camping. In this camping there are also houses to rent but the "tent pitches" seemed to be more in a forest, on some nice small hills.
CHM has also a "center" but with less shops and restaurants than in Euronat. Most of them make afternoon break (they close between lunch and dinner time). Closer to the beach you can meet much more naked people. There's also a small aquapark near the beack exit with a few water slides and pools. They don't have much animation programs, but I managed to attend one water aerobic. It was't very professional, it was without music and the trainer also didn't show much. There were more lifeguards around the pool looking after the safety and if people respect the rules (e.g. at the slides), The lifeguards demonstrate good example, they also did not wear clothes or just a T-shirt or walkie-talkie.
When going to the real beach you pass a small house where a guard sits and remind the people not undressed yet that that is a naturist beach so they should take off their clothes already here. In the other dircetion they control if we are guest of this campsite (you have to show your camp-ID or your day-pass. Also on the beach the lifeguards (also naturists) remind people who are not undressed (e.g. walkers coming along the beach from other campings) that it is a naturist beach.
In both campings I was not satisfied with the cleanliness in the public toilets/showers. Toilet lids were missing, mostly there was no paper and no soap.