Ah 9m, ok, that's bigger than it looked on the video. As long as the boat is longer than the waves you are dealing with you should be relatively stable.

You are, still pretty scary at first. I tried our kayak for the first time this summer at sea, maybe 1 m waves or so. Boat is 5 odd meters, and at first it fleet scary, was fun afterwards so! Quite a change after lakes, rivers and maybe some wind at most. Being sideways, you have to return at some point, was adventurous for a noon at sea kayaking like myself!