Tying off the tiller while you bounce around on (or off) the foredeck can have bad results. The safest thing to do might be to
rig a downhaul for the
jib. With a
line attached to the halyard
shackle and led through a block at the tack fitting and then aft to the cockpit, you should be able to throw off the halyard and then pull the
jib down without leaving the cockpit. You might be able to use the downhaul
line to hold the lowered
jib in place on deck by lifting your end of the
line over the bunched sail and then hooking the
line under a guy hook or other fitting further aft, before cleating it off. You''ll have to figure out where the hooks would need to go, but it''s a lot safer than wonderding how long you can tread water while the boat sails on.