[mabarker1]

http://www.corecomposites.com/composites/reinforcements/

Data on CFHC

SG is 1.8 so just under 2x H2O SG

So it would require additional trapped air to float.

[Chgogal]

Indian Ocean Currents

http://www.oceanweather.com/data/

[leakinInTheBlueSea]

I’m seeing honeycomb panels starting at 2-3 lb/ft^3 on that site... that certainly floats.