Hm. I would imagine the foam is high strength, but low density.
High density would kind of defeat the purpose.
High density would kind of defeat the purpose.
edit--I just checked, the type of foam used ranges from about 20 to 45 lbs/ft³. That qualifies as high density.
I was _going_ to claim that water is denser still, way down deep in the ocean. But I thought I'd check it out first, and although I'm not well-educated enough to understand the important parts of phrases like "At 0 °C, at the limit of zero pressure, the compressibility is 5.1×10−10 Pa−1", I can understand this phrase: "The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume."
http://en.wikipedia.org/wiki/Properties_of_water#Density_of_...
[1] http://en.wikipedia.org/wiki/Properties_of_water (see sidebar)
Silly me.
I was trained as a physicist, not as an engineer, and to me "high density" means "lead". :)