Just another vote for enabling the swimming wrist HRM on the device.
Over the weekend - wore it without starting Pool Swimming activity - leaving to MoveIQ to recognize activity in the pool.
HRM works this way and works great.
I invite others to test it and put more pressure to Garmin to leave this options to users to decide if they want it enabled during swimming.
I will never wear a strap in the pool, and have right to decide if I want wrist based HRM during swimming.
iWatch and Suunto both provide this out of the box.