I have worked out how to be alerted to phone calls when I swim with an apple watch
Despite trying all sorts of things, I have been unable to be reliably notified of incoming phone calls on my apple watch while swimming, but I have found a useful work around that I hope will help others.
I have learned that when swimming, my apple watch does not vibrate and no notification of the call is left on my device. I understand that this is because transmission of cellular, wifi and bluetooth is very poor through water. I also understand that for some reason, notification of a missed call can only happen on one device, and when I swim, the notification defaults to my iphone which is out of the water. What does work is that every few laps, I can check if there have been any incoming calls or voice messages. I click on my little green phone icon, then click on recents and also voicemail. Any recent incoming calls or voicemail messages are listed there, and I can return the call. For privacy reasons, I get out of the pool and return the call on my iPhone, but I could return the call on my apple watch if I wanted to. I find that I am able to return calls within a few minutes, and everyone is happy. I also feel very secure that I will not miss incoming calls, so I can relax and enjoy my swim.
What may work better for others, but is not an option with my work, is to request that text messages be sent instead of phone calls. With text messages, my apple watch vibrates, and a notification and the text message itself is left on my watch, and I can reply when I get to the edge.
It may sound like a real drag to receive text messages or check for phone calls while swimming, but it makes it so that I can actually swim without anxiety when I am on call. Otherwise I would not be able to swim, which I would really miss.