While "sprinting" in a boat exclusively by using the sprint key (ctrl by default i think), get out near land by sneaking (shift) and the player retains sprinting speed along with the higher dynamic fov effect. Even after releasing movement keys, jumping, sneaking the speed increase will remain until the next 'start' of running followed by stopping happens. This essentially allows for infinite sprint on the ground (it slows you down to normal speed when jumping or falling but doesn't end the effect), It even doesn't seem to drain the hunger meter, though uncertain.