If you are looking for a (very, very) cheap alternative to the almighty Navitimer, this lovely model from Casio might just be the machine that you're looking for. Rated at just under 100 USD on the Amazon.com, this timepiece has the usual famed Casio quartz precision associated to a quite precise slide rule computer.
Besides the slide rule, it has a chronograph function (no split time, tho), a screw-lock crown and it's water-resistant up to 100 meters, which is more than enough for a watch that is not intended for underwater activities. There's a very interesting review of it on the Forum Watchuseek, posted by the user Nanok.
Although fun to use, the slide rule is not that intuitive. You have to train to understand the logic within it. The Casio Web Site has a page loaded with simple examples here.
And if you look at the Wikipedia, you'll find this page loaded with information about it. If you dig deeper, and also in the Wikipedia, you'll find a page devoted to the E6B flight computer. This later one is, basically, the slide rule that is present on this Casio watch.
This is a very handsome watch and my personal experience with it is quite positive. For such a cheap equipment, its precision is astonishing, either in the quartz machine and in the slide rule computer, which is quite accurate (it's Japanese, after all). Although with a large dial, this watch is quite light on the wrist. Doesn´t bother you at all. The luminescent hands, however, are not the best. In fact, they are quite weak. So, it's not that easy to see the time at night and in an unlit neighbourhood. Also my 43 years old eyes are no longer what they used to be, for very short distances viewing. So be warned about that if you suffer from the same problem, because the slide rule engravings are really small. I think it's time for me to buy my first glasses, since I'm reaching for a loupe quite often, when using this watch for calculations.
All in all a nice piece of watchmaking. A great one, if we consider the price. It's a Casio, is it not?