Today I concluded testing of the Tic Tac box I have prepared. Plexiglass on the bottom in front of the camera lens. Secured with silicone. The lid also sealed with silicone. That wasn't enough so I also sanded the outside of the lid with grain 800 and then applied a layer of lacquer. Around the box and the lid I inserted some Vaseline. That seems to work.
Some pictures from my test:
After two days of submersion I didn't find any water inside the Tic Tac box. So I believe I am ready to put the camera inside.
Thanks to Tic Tac for helping me getting a Tic Tac box