WAMIT gdf 3D format

The GDF format is from the WAMIT software, a computer program based on the linear and second-order potential theory for analyzing floating or submerged bodies, in the presence of ocean waves. It is a plain text, human readable, format. It consists of a 4 line header which includes the number of quads that are in the file. Each quad is simply a list of each vertex, so each line(after the header) consists of 16 floating point numbers. Whether a triangle can be represented by making the last two vertices identical is unknown, probably application specific.

2 body structure
1 9.80665 ULEN GRAV
0 0 ISX ISY
400
6.618034 11.175571 -19.000000 7.000000 10.000000 -19.000000 7.000000 10.000000 -20.000000 6.618034 11.175571 -20.000000 
6.618034 11.175571 -18.000000 7.000000 10.000000 -18.000000 7.000000 10.000000 -19.000000 6.618034 11.175571 -19.000000 
6.618034 11.175571 -17.000000 7.000000 10.000000 -17.000000 7.000000 10.000000 -18.000000 6.618034 11.175571 -18.000000 
6.618034 11.175571 -16.000000 7.000000 10.000000 -16.000000 7.000000 10.000000 -17.000000 6.618034 11.175571 -17.000000 
6.618034 11.175571 -15.000000 7.000000 10.000000 -15.000000 7.000000 10.000000 -16.000000 6.618034 11.175571 -16.000000 
6.618034 11.175571 -14.000000 7.000000 10.000000 -14.000000 7.000000 10.000000 -15.000000 6.618034 11.175571 -15.000000 
6.618034 11.175571 -13.000000 7.000000 10.000000 -13.000000 7.000000 10.000000 -14.000000 6.618034 11.175571 -14.000000 
6.618034 11.175571 -12.000000 7.000000 10.000000 -12.000000 7.000000 10.000000 -13.000000 6.618034 11.175571 -13.000000 
6.618034 11.175571 -11.000000 7.000000 10.000000 -11.000000 7.000000 10.000000 -12.000000 6.618034 11.175571 -12.000000 
   ...
   ...
   ...

A comprehensive description of the format can be found in chapter 6 of the WAMIT manual.