The purpose of this study is to determine how to incorporate a smart water bottle to improve bladder filling for prostate cancer patients undergoing radiation therapy.

Inclusion Criteria:

• Age older than 17 but less than 81.
• Non-metastatic prostate cancer patients undergoing definitive radiation treatment.
• Patients that self-identify as "smartphone owners".
• Patients with either iPhone (iOS 13.0 or higher) or Android (version 5.0.1 or higher) based smartphone access.
• English or Spanish speaking patients.

Exclusion Criteria:

• Patients with any history of pre-existing urinary retention.
• Patients with any history of kidney, urothelial tract or bladder cancer.
• Post-operative prostate patients.
• Patients that plan to be treated with pelvic lymph node radiation coverage.
• Patients without a functional bladder.
• Patients with a history of prior pelvic surgery or penile augmentation (circumcision is okay).
• Patients who have previously received any form of pelvic radiation.
• Patients unable to give informed consent.
• Patients who refuse to drink room-temperature water used for bladder filling.
• Patients without functional vision.
• Patients who are colorblind.
• Patient who refuse to use the smartphone app or who refuse consent.