You don't have to be in heavy weather to use jack lines and a tether. Last year I was leaving Lake Tasmoo on the Vinyard, a perfect day wind at about 6 knots and the water was calm. I steered the boat into the wind and went forward to raise my mainsail and when returning to the cockpit the wind shifted slightly, got hit gently by the boom and over I went! I found out why they call them lifelines when I caught the back of my knees in them and saved myself from going completely over. Hair in the water and one hand on the lifeline I got myself back on board. All that happened was brjuised legs and pride. Now I go forward I hook up, period!