"It was a surf beach so he might well have been dumped by a wave and knocked out, we don't know. The post-mortem will hopefully tell us something and that will happen in the next couple of days.''
"He was a strong swimmer, he was a surfer, he wasn't out of his depth in that way, he knew what to do. But who knows.''
She said Peter's father Bob, who had flown over to Spain, would arrange Peter's cremation there before bringing him back to their Taupo home.
Mrs Stenhouse said her family would remember her son with a private service at the top of a New Zealand mountain.
"It's not going to be a funeral, because Peter was a very quirky different sort of person, he loved travelling, loved the outdoors so we'll go up a mountaintop somewhere and say our goodbyes.''
The "quirky'' traveller, who grew up in Upper Hutt and attended Massey University, once dried his underwear on his handlebars while he biked around Europe, she said.
"He was on a bike and was literally living day to day with what he had and was knocking on farmhouse doors and finding people so amazingly welcoming. He just made his way around on his trusty bike.''
Peter had been based in London periodically over the last three years and was working at Fifty Nine productions creating animated backdrops for theatre, modern operas and ballets.
He produced work for high-profile performances such as Les Miserables.
His girlfriend, originally from Hastings, planned to return home after packing up her apartment in Madrid, Mrs Stenhouse said.
She said Peter's sister would fly over from South Africa for the private service, so they could remember Peter as a family.
"Apart from being adventurous he was also, playful, inspiring and had a zest for life.''
Check out some of his work here.