A Russian company called Infratech (Инфратех) has developed a thermal scope (model IT-615 VM (ИТ-615 ВМ)) for the special forces divers. It can withstand a long time of salt water exposure and submersion into the water for up to 20 meters. This thermal sight was introduced during the ARMY-2017 arms exhibition.
The advantage of such a scope is that the divers won’t have to detach it from the firearm and keep in a separate sealed compartment while being under water. They can keep it mounted on the weapon and be able to immediately use it once getting out of the water. The buttons and other controls are also sealed and allow adjusting or changing the settings while being submerged. The controls are also optimized to be easily reached with the diving gloves on.
The manufacturer’s website has similar commercial scope listed. The difference in model designation is that the military model has two additional characters at the end. Possibly the military model is based on the commercial one or it is the same one with just a different model name. The scope available on their website has an MSRP of $9,731.
Interesting to note that demonstrating underwater military products submerged into a fish tank is kind of popular in Russia. If you remember, several years ago they’ve introduced the ADS amphibious rifle in a similar manner. Cool idea though.