The 1st district covers most of both shores of Lake Ponchartrain but then cuts across Lake Borgne (no connection of any sort exists there) to cover the eastern bayou as well.
If you wanted to create a road connection, LA-01 would have to pick up the two eastmost New Orleans precincts, 9-45 and 9-45A. They have about 1,000 residents between them and are majority non-Hispanic white. But former Congressman Cao lives in one of those precincts in the Venetian Isles neighborhood. Perhaps they didn't want to draw him out of the New Orleans district or into a Republican district where he might challenge the party's man.