It's a shame that this didn't turn out better for you. Photosynth works by matching textures between photos, but the boat has no real texture to speak of and the water is different in every shot. The only thing that Photosynth stood a chance of matching between these particular photos was the clouds and coastline in the distance.
I hope you'll come back for another go at Photosynth, next time perhaps with photos of something stationary with lots of visible texture.
For more tips, check out the photography guide at this link: http://photosynth.net/howtosynth.aspx
All the best to you.