if you have doubt on autoCAD use Rhino3D , its a good software for boat design . yes it is true that you can build curves directly by manipulating...
im not sure if there is really a Mac kayak design software , but you can find it on some search engines , i mean try searching for it .. try...
yeahh a website to support those things you've just listed , do you have ?
Silo , use it .. its affordable