Perplexing strobe issue

Hi.  I am using an Olympus TG-5 in an underwater housing and with a YSI-03 strobe on a remotely deployed baited camera stand to collect data on juvenile fish.  The strobe is set to fire every 30 sec. over a period of 1/2 hour.  For the first 18-20 minutes of the deployment, the strobe and camera work beautifully.  Then, the strobe skips firing every second image through the rest of the deployment.  Any ideas on why the strobe would take longer to recharge after two shots after working so well?   I work in Alaska, where the water temps are usually around 46 F (8 C).  My initial thought was that the cold might be affecting the battery on either the strobe or the camera, but in that case I would have expected it to miss every other shot, not every second shot.  

Anyone have experience with cold water photography with similar equipment? 

Thanks!

It would appear that it is slow recycling is it's missing shots.    So when you say it is missing every second shot, do you mean that it takes two shots then misses one?  I would still think that could be slow recycling.

Some extra detail would help for suggestions,  What settings are you using on the camera?

What power is the strobe set to? It may be discharging the battery to a level that makes it take longer to recycle. You could prove this buy selecting a different strobe power and analyzing the results.