How to use Egyptian Pontoon Ferrys?

[Boisforas]

Yes, move them to marsh for loading / unloading.

Now Im really confused: the ferries only work in marsh hexes? Why include them in the unit mix if all they do is bridge marshes. Didnt the Egyptians hose down the sand walls on the Israeli side of the canal so they could use the ferries? How am I supposed to get the Egyptian armor included in this scenario across the canal? What am I missing here? Eric