I feel like I'm doing something wrong. I always missed and only got two silent dice which are not helping me hit anything. Once you hit, you can keep hitting as long as you see what the enemy rolls I suppose.
The pixelated text is hard to read. Especially white on white shimmering water, thicker outlines or a higher resolution would help.
In the help screen you show several walls of text... In general a more interactive tutorial or simpler gameplay would be better. Like just show some help for each action when you can perform it and explain items when you get them.
It's a nice innovative idea though and fits the theme well. Maybe something with fog would have been a good idea: A duel in a mostly fog covered arena where you can sometimes see the enemy, the rest could maybe stay the same.