This is a maneuver that Jeff McGovern and myself developed together as a ‘think tank’ and ‘R&D team’. It’s called the ‘Combat Position’, and it’s possible to execute only in a W Kayak:

Upon realizing that you have a business with a big fish you need to swiftly reposition yourself along the saddle in the riding position (‘Mounted’) and as forward in the cockpit as possible, with your knees tucked into the front hull tip openings – see ’1′ in the illustration below.
As a result of this change in weight distribution your W kayak’s bow will dip in the water (see ’2′) while the stern will come out of the water (see ’3′).

In this position your W kayak will be ‘planted’ in the water and offer maximum resistance to unwanted change, whether such change is tilting sideways or going forward.
Being in this position will free you from the need to balance your kayak while you’re fighting the fish, and let you focus on your fish whose capability to outmaneuver you was reduced to almost zero.

All the fish could do now is swim forward or sideways, and since your W kayak will generate a lot of drag in this position the fish will soon get tired and become less of a problem to reel in.