  SNO+ is a neutrinoless double-beta decay ($0\nu\beta\beta$) search experiment
using 780 tonnes of tellurium-loaded liquid scintillator. The experiment is
currently collecting data in the first of three planned phases, in which the
detector is filled with ultrapure water. During this phase, the cleanliness of
the water can be assayed using in situ measurements of $^{214}$Bi and
$^{208}$Tl (daughter nuclei of $^{238}$U and $^{232}$Th, respectively). These
results will both inform preparation for scintillator fill and support water
phase physics analyses like the search for invisible nucleon decay modes.
