The swan mussel has a thin fragile shell. It is found in fresh stationary waters. It has a foot so that it maneuver a bit. There is one known incident of a swan mussel which ended up on the bank after a mechanical cleanup and 'crept' back into the water. However, this is a rare incident; swan mussels don't usually move more than a few centimeters. You can often find pearls in these mussels.