I have had two Ronstans, both of which were generally good. The first was the fancier model with the larger digits and the buttons on the face of the watch. I was happy with this one but it was comparatively expensive and the band broke after only one season and I have not yet found a replacement to fit it, although I haven't looked too hard.
RF4030 |Ronstan Marine Division
The other one, which I am using this season is the one that you mentioned, I think. No moisture problems, so far, and I have raced three times in the rain so far this season. The downsides are that the digits are smaller and the buttons on the side of the watchface can be accidentally pushed by your writst or another watch. (I also use a regular watch with a second hand to help me time the beginning of the starting sequence.)
The best of luck.
RF4031 |Ronstan Marine Division
Edit: I neglected to mention that I have also used a digital egg timer that I bought at walmart for three or four bucks. Won't beep at 4 and 1 minute but will keep track of the time without a problem.