The regular Fitbit is not waterproof but features a water resistant design that allows the user to wear it in the rain and sweat without causing ill effects. Fitbit owners are not recommended to swim or shower while wearing a regular Fitbit device.
As of 2015, the Fitbit Surge and the Fitbit Charge are both water resistant up to 50 and 10 meters, respectively. Owners of either of these devices can submerge them up to their recommended height without causing damage or function to cease. Both the FitBit Surge and the Charge are not designed to withstand swimming pressure and the company recommends that users do not swim with them on.