I am looking for my first HRM and was wondering which is a good one to get. I have been looking around the forums and have found many recommendations, but none of them say whether or not they can be worn while swimming. Is this because it is a given and all of them can be worn underwater? I want to make sure I am training in the proper zones and all of that. I am thinking about the Polar FS1...I just need basic functions. Any thoughts?