An accessory kit for use with a wearable medical device, such as a wearable defibrillator, that includes a control unit and a first plurality of electrodes electrically coupled to the control unit. The first plurality of electrodes includes a first plurality of ECG sensing electrodes and a first plurality of therapy electrodes configured to provide a defibrillating shock to a body of a patient. The accessory kit includes a waterproof enclosure configured to receive the control unit and protect the control unit during operation in a wet environment and a second plurality of electrodes that are electrically coupled to a connector configured to removably and electrically couple to the control unit. The second plurality of electrodes includes a second plurality of ECG sensing electrodes and a second plurality of therapy electrodes configured to provide a defibrillating shock to the body of the patient.