Chronosport UDT Sea Quartz - Sylvester Stallone - Rambo III
There are many variations of this interesting watch. Rambo wears the version with black pvd case, Arabic numerals on the dial, a 4-digit digital screen, diver's bezel (with 10, 20, 30, 40, 50 markings). The movement is from Breitling.
This particular model is very hard to find, I can't even find a photo of this particular model, except the screenshot from the actual watch in the film (thanks to productplacementblog) which shows the details. Other similar models (usually without the arabic numerals) can be sometimes found on eBay.