
M400 a mare
I recently bought this Polar M400 and I have 2 questions: 1. I notice that the battery doesn't last long, what can I do to increase it? 2. I have to go to the beach tomorrow, can I use it? I saw that it has an open water mode, but the back of the watch where the charging cable plugs in is exposed and I'm afraid that if salt water gets in it, it will ruin it.