As promised I have crafted a homonym riddle just for @Duck. With the recent spike in homophone riddles, I figured it was time. I finally figured out what word to use, so can you tell me which word it is?
Depart quickly, turn back now; this little riddle is going to be foul.
Take a plunge, into the fire; like learning to walk on top of a wire.
Don’t cower, nor cringe; there’s no need to fear; solving this riddle, won’t take a year.
Tipping already? Biting your nails? The next clue is, I am used within sails.
Help is here, an unsung hero; also known as batsman’s zero.
If that’s not enough, then I’ll get you out; my vehicle floats, there’s no need to pout.
One last clue, before I must leave; defined as another, a mollusk I be.
What am I?