It is possible to walk around some sections of Bassenthwaite, but there is not a complete circular route. It can get boggy, particularly in the autumn and winter. Some sections of the lake shore towards the southern end of the lake fall within farmland, with no public right of way, so you must pay careful attention to signage on display.
The sections that you can walk on are mainly low level with beautiful views across the water. There are plenty of wildlife spotting opportunities here. Many birdwatchers come in the hope of seeing an osprey.