Dear Jo
it is nice... but i agree with wanting to add a touch of something...
the first thing i thought of was sun - wouldn't have to be the orb, but changing the light. this can be combined with the valid observations on center of interest:
you mentioned "adjusting the sky colors a little"
i think that if you did exactly that, creating a little more contrast, it would jazz it up quite a bit without altering content significantly, or causing busyness. do it so as to provide a focal point within the clouds as well as a sort of visual movement towards that point, it would create a center of interest, without actually inserting an object, like rocks, or a boat, or the sun itself, all of which i think would distract from the existing softness... and quite possibly detract from the piece.
the other thing i thought right off is rather subjective. i personally find the centermost and "furthest" portion of the sea a little flat... no need for big waves, but i think a little more texture there would do nicely.
good work. it is pretty even as it is. when i used to paint i was often very hesitant to go adding or reworking after a certain point... destroyed a couple of things that way. imho, art is above all an emotional channel... and if this painting feels a little empty to you, perhaps that is what you were expressing when you did it?
~ waves ~