I would understand if retrieval had been explained as impossible in the narrative, but it just seems to slip everyone's mind. I would doubt every canister was destroyed in the crash, and I'm sure the "famed Starfleet engineer" could have come up with a way to salvage a few canisters.
At the start of the episode we see the ship sinking into a large body of water, a bay or cove or something. Without underwater breathing equipment or a transporter, it would have been impossible to swim into the ship retrieve the canisters. Even if the ship was sitting in only 100 feet of water (the ship is 18.32 meters tall or about 60.1 feet), noone could have held their breath long enough. Admiral William Thomas Riker 17:53, July 27, 2011 (UTC)
- Not to mention the pressures of the water and such. Divers have to take many precautions to avoid getting decompression sickness (colloquially known as "the bends"); there's no evidence they found the kind of equipment they'd need to prevent and/or cure this deadly condition. The novelization The Dominion War, one of the Jem'Hadar refers to "the planet's many deep pools."