Apple Watch Series 5 (GPS) 40mm Aluminum Case with White Sport Band - Silver - (2019)

I would recommend going to the Apple site and watching the video about Apple Watch. I have used an Apple Watch for years and have this $399 version. I use it to show temperature on my watch face as well as my activity progress, time and date. I really enjoy the fact that it shows my activity - how many calories I have expended, how many minutes I have exercised, and how many hours I have stood.. It does a great job with showing texts, controlling music or audiobooks that are playing on the phone, tracking work out whether at the gym or walking outside. It will show a map of where are you have walked outside. it also shows incoming phone calls and calls can be answered or declined from the watch. it is a powerful and enjoyable little piece of technology.

No, the GPS only models use your iphones internet. The GPS + Cellular models have their own internet (data) but you have to pay for it though your cell phone carrier.

yes they are water-resistant as well as there is a button that you press on your watch after you are in the water. "Swimming metrics. Strokes of genius. Water-resistant to 50 meters, Apple Watch Series 5 is designed with swimmers in mind.1 The Pool Swim workout automatically records splits and sets and can actually recognize your stroke. The Open Water Swim workout visualizes your route on a map. And both precisely track active calories, distance, and overall pace." - apple. There are a lot of articles you can look up online about it. Yes you can change the bands however you have to buy the different bands wanted.

It doesn't have a clip--I think it has to be worn as a watch.

Yes. Go into the Watch app on your phone. Then Display & Brightness, then switch Always on to off.