He wants to play (or is hungry/thirsty)!
This shows several signs that your dog desires to engage with you, such as:
- tail wagging
- physically engaging you by "pawing"
- occurs when you are not focused on him (instead, on your phone, sleeping, or swimming)
When this happens, I encourage you to play with him, dogs - especially younger ones - need constant healthy play and exercise.
It can be as simple as throwing a ball as fetch or running around with him.
There is also the slight possibility that he is hungry or thirsty, and he is trying to get your attention so you refill his food and/or water. Without much context in your question, I can't say what your dog is trying to tell you. Just to be safe, make sure he has had all necessary food and his water is full before playing.
This answer is from my personal knowledge and experience. No sources are listed, but more information is available on the internet by Google to back me up.