Not for water activities like swimming, it 

The red light of the indicator is always on, the signal is too weak, please adjust the position and direction of the device; The red and blue indicator light is flashing fast alternately, the device has not detected the SIM card, please confirm that the SIM card is inserted. If the SIM card has PIN turned on, you need to insert the SIM card into the phone to disable the PIN code first and retry after inserting the device; red and blue lights flashing alternately slowly, insufficient traffic or unpaid stop, please replace the SIM card or top up; 

Yes, it comes with a SIM card and 100M of free traffic for the first setup 

Yes, it comes with a sim card. 

Hello, unfortunately no, you cannot insert a SIM card in this smartwatch.