The mono braided loops are not a good choice for salt water flyfishing. The come un braided and are not that strong. There are some kevlar braided loops out there that are stronger but very stiff.
I wold suggest using an albright for leader to flyline.
I tie a 3 foot section of 40 lb to the flyline with an albright and put a surgeons loop in the end. Then you can put a loop in a section of 15 and loop it right to the 40 lb. and tie on the fly.
You can also taper down from the 15 lb. to 12 or 10 with another albright .