While removing my diving computer back on the boat, I lost the part that closes the bracelet: the design of the whole bracelet could be improved, it does not withstand efforts very well.
So back home, I used OpenScad to redraw the part, and reprinted it: that's it !
I hope it will be useful to other divers.
Have safe dives, and always secure your computer to your wetsuit using a secondary method.
Should print in ABS to be able to withstand water.
PLA does not support water very well on the long term.