It's interesting that the first time we hear about Pluto, it's in Alabasta - a desertic country in a 3 years long drought, which primary struggle is the control of water as a ressource ; but then Pluto is associated with Water 7 and Wano ; two islands where water is extremely abundant, overflowing and threatening the very land.
Pluto is the roman god of (mineral) wealth and fertility and ruler over the dead, an adoption of Hades, the greek god-king of the underworld, as well as a conflation of Orcus and Dis Pater (or Di(e)spiter). (Roman mythology is always a bit wonky, because the Romans were heavy-handed with the syncretism.)
Between a land that has been stripped of its water, and two who are drowning under it, all 3 heavily weighted by death and misery (past and present), there's probably a message about balance somewhere.