probably from sand from the deserts near by...
That would be the deck.
The "main" refers to the ocean and "bounding" describes it's action as felt from the deck of a sailboat.
People sailing on a brig were not in the habit of riding the deck on any vehicle. Below deck it would have been even totally impractical.
no sailing is required
There is no convention for it nowadays but it used to be the medical deck on a man'o'war to disguise the blood on the deck
They both use a deck.
Yes
Tabernacle
It is usually the rear raised portion of the deck on a sailing vessel
tabernacle
The bilge.
When it has a broad and slip-free deck, including rails that allows it. Power boats are made fro speed and it would be unwise to attempt to stand on the small deck are at speed from danger of being thrown off.