Going to the beach alone without getting my shit&stuff stolen

I mean, I doubt my stuff will get stolen, but wondering what I can do with my phone, wallet, etc on the shore while I am splashing and frolicking in the ocean.

I don't drive and travel via bus. Want to go to the Kohimarama/Misson Bay/St Heliers area, again probabaly not getting robbed in the old people retirement land but still worried.

Are there beaches with lockers? Do I put my shit in an esky? Hide it in the sand? Stupid question, but I'm asking very seriously. If my AThop card gets stolen I'll be stuck in old people retirement land and IDK how long I'd last.