Spin ice materials exhibit novel magnetic behaviour because of their atomic interactions and geometric constraints of the crystal lattice. This novel behaviour takes the form of emergent quasi-particles that behave as magnetic monopoles. We propose to study a spin ice material (CdEr2Se4) that differs in structure from conventional spin ices. Recent ac susceptibility measurements in an applied DC magnetic field on CdEr2Se4 have found previously unseen behaviour indicating two relaxation mechanisms. Our aims are: Firstly to use muons (amongst other techniques) to understand the nature of these relaxation mechanisms, as well as their temperature and field dependence. Secondly to search for spin dynamics at very low temperatures, where one would expect no dynamics in a classical (non-quantum) system, behaviour that has been observed before in other spin ice materials but not yet in CdEr2Se4.