‘‘There are people who do attempt to play here and fish here,’’ says Everett marine police officer Patrick Johnston. ‘‘For some it's some sustenance to feed their people. But more and more people are using the river for recreational purposes.’’ Here, Jimmy Kittery gets a taste of the Lower Mystic Lake while tubing behind his dad's motorboat on his 14th birthday. The river flows out of this lake on the Arington-Medford line.