Nice composition and your 10 stop filter works well with the flowing tide. Your horizon might be a little off but I'm sure you can correct that when printing your shot.
Thanks everyone for your comments. I have the first version of the Hitech 10-stopper which is only really useable for mono as the blue colour cast is so strong - but I now have the long exposure bug so have the new "Pro Stop" version on order which is reported to be much better.