SNO+ is a large multi-purpose liquid scintillator based experiment, with the main physics goal of searching for the neutrinoless double-beta decay of 130Te. The first of the three SNO+ phases started in May 2017, with the detector filled with ultra-pure water. The deep underground location (6000 m.w.e.) and the low background levels allowed new physics searches, together with the measurement of the 8B solar neutrino flux in the 5-15 MeV energy range. Recently, SNO+ has began the transition to the scintillator phase. The double-beta decay phase is expected to start in early 2020, when the ultra-pure liquid scintillator will be loaded with 3.9 tonnes of natural tellurium, for a half-life sensitivity larger than 2×1026 years in 5 years of data taking. This article focuses on the low background measurement of the initial water phase.