Performance: No Water Resistance: Maybe.. depends hugely on the crack. If the crack is passing through the entire glass thickness then your water resistive capabilities are gone. If it's just a hairline crack then no problem. You can have the back panel replaced at Samsung service centre. They are quite cheap and will get your water resistance back.
We apologize for the inconvenience caused. We would suggest you to visit nearby Samsung Service Centre so service engineer will examine your device physically. Please find service centre details in the link provided http://www.samsung.com/in/support/servicelocation/
