Yet the descriptions in Genesis do make a reed boat a impossibility.
You also did not source the gopher wood showing how many scholars quote some kind of wood verses only 1 translating it as reed, as shown below.
The authors clearly describe a wood boat, a boat that should remain in mythology and theology, as it is not a practical boat that could exist outside literature.
The proper translation is probably that of "squared timber".
I like how you imperially declare that "the descriptions in Genesis do make a reed boat a impossibility." You don't have any thing to justify that statement. You just want to interpret it as a wooden boat so you can make it impossible.
1) GPhR probably came from the earlier semitic word GPR (without the much later added vowels)
2) Wood can be translated Stalks such as reeds stalks.
3) The word sometimes can be translated reeds, as also stated in
Before the Flood book
4) The only other use of ark involved papyrus reeds.
5) Arks were coated with pitch, wood boats were caulked in the seams with pitch, as shown by archaeologists in Ur.
6) Arks held as much as boats, but were unsinkable. See Thor Heyerdahl's
RA and
Early Man and the Ocean books.
7) Reed boats could be made 450 feet long.
8) Even the Sumerian/Akkadian accounts put many storied structures on the top of the raft.
9) Since the Hebrew word for world can be translated region, the Ark could hold the animals of the region of the Sumerian flood plain.
The Reed boat is scientifically, historically and Biblically valid, the wood boat of 3000 BC is not. Most people translated it as wood because they had no knowledge of reed boats. Thus, your more common translation argument is invalid.
Watched a long preview trailer yesterday when catching RoboCop (not as bad as reviews) and it is one of those movies made for the big screen. 
