The plywood floor helps a lot, especially in the middle section where the "V" hull is more noticeable. I still won't take this boat into the salt water. I think it's too light to handle the currents and the winds.
A mile off shore is a long way! I have taken a 15 foot sailboat out that far as I had more confidence in it's ability to float, even upside down (via first hand experience) but I won't go that far out even in my fiberglass 15 foot outboard. High winds push that boat around too.
As Jason L. stated, I have been in larger boats out in the ocean in some pretty good size chop and still had to sit and grab on to something while moving.
If you're set on going out in the salt water here in So Cal, I think a 16 foot plus deep V is the minimum I would take IMO. Now that I have a vehicle that can tow something that big, I need the space to store one which is the reason I have smaller boats. There is hope though. My son is planning to buy a larger house!
Keep it safe.