Whanganui resident Allan Wrigglesworth was surprised to find large clumps of what he called "white fat" washed up on northern parts of Castlecliff Beach near Kapiti Terrace on Sunday morning.
Wrigglesworth, who lives nearby and was out for a walk, said he made the discovery around 8am.
"Getting fat up here is unheard of," Wrigglesworth said.
"This isn't next to the [Whanganui] river mouth or on South Beach, this is kilometres away.
"There has been fat on the beach before, periodically. It's usually only 5 millimetre little pellets though.