I would go a little further with the layout before putting it together. I really like your two accent fabrics of the jumping whales and the seaweed and really think they need to be used in this quilt but where is the question. I think they might look good as outer borders and go with layout #3 for the inside of the quilt. I would want to see what it would look like to continue that sequence of piecing around your panels as well as between them then try to use the seaweed and whales as two accent borders and tying it all together with maybe some more water fab as the outside border. But I would really want to see that laid out before committing to the sewing. Sometimes what we imagine will look great looks downright awful when we actually lay it out and see it for real, at least with me any way.