What is a "Surf Mattress"?

Question

I have been surfing most of my life, but I have never heard this phrase. I came upon it while reading about George Greenough. There are no clear definitions on the web. From what I can gather, it is possibly an old school word for a knee board? I believe the phrase to be austrailan and I know it is from the 60's.

Answer 1

“The Otter,” a 6’5” by Rich Pavel concave stringerless, “The Disk,” a Dave Parmenter bellyboard designed for a certain boutique wave, and “The Neumatic,” an inflatable air mattress all claw their way to the surface for this (hopefully) recurring look at non-traditional wave craft. What might we unearth next? Plenty. The New Democracy in equipment is revving, and we struggle to think of a downside.:-)

Answer 2

It is (was?) an inflatable raft about four feet long by two feet wide, internally divided lengthwise by baffles into four or more parallel chambers. Quite common before bodyboards became popular.