You can use the Insta360 Nano in wet environments (and probably underwater) with this water-resistant housing.
360 photos and videos in water or underwater can be fun. You can use the Insta360 Nano for photos and videos in water with the Ricoh TH-1, a water resistant housing for the Ricoh Theta (the TH-1 is discontinued but the Ricoh TH-2 appears identical). Apparently, the TH-1 can also fit the Insta360 Nano if you use the Nano Mount tripod adapter ($30 to $35; reviewed here).
Here is how a video from the Nano looks when used with this housing.
The case adds quite a bit of glare and reduces contrast, so I wouldn’t use it unless I had to.
Ricoh says the TH-1 and TH-2 are not waterproof and only have an IPX7 water resistance but I’ve tried submerging it in a bucket of water and the water did not enter it. There’s also a couple of 360 videos on YouTube of the TH-1 being used underwater at a shallow depth (videos by Danny Chung):
Please note also that the refraction changes the effective focal length of the lenses and makes the stitch much rougher.
I plan to try the Nano with the TH-1 case the next time we go swimming!