Nan Matol - but a pyramid?

SOURCE FOR THIS PICTURE: Henry Jones' blog

On P. Kent's website we read that Harry Mason wrote in 1989:

"In 1978 I was working in New Guinea on a mineral exploration project. Whilst at an expat club in Port Moresby one night I saw an 8mm film of a huge stepped pyramid city that was built like Venice with canals. Some 2/3rds of this massive affair was buried in the nearby Lagoon but could apparently still be seen with scuba gear. The film showed a yacht sailing down a "main street" canal with temples, houses, and pyramids for miles on either side sticking out of the jungle. The canals formed a regular interlocking grid - just like a typical USA city block system. Examination convinced the researcher that this city was designed and built with canals and had not just had it's roads flooded.

The film was shot by a sailor and his family who had toured the Pacific researching historical sites - I believe that the city location was on an island in either the Marianas or the Caroline Island Groups - sorry cannot recall exactly which one.

My main point on this is that all the structures were built from basalt and showed precision leveling of the rock surfaces, whilst the building structures were amazingly orthogonal. These strongly resembled the recent web site photos of the structures located underwater south-west of Japan. Perhaps someone has documented this "Venice" in the present day literature on Pacific Archaeology - re stepped pyramids and boat travellers from South America ???"

As Mr. Kent points out, this is probably Nan Matol (Madol?)... any other theories?