When the cute little boat chugs out to Elmer, its gun barrels are already extended. When he picks up, it extends them again and fires.
When Elmer fires his double-barrel shotgun, both barrels appear to fire both times.
After shooting the shotgun, Elmer never has to remove the spent shells.
Mel Blanc (as Daffy) mispronounces the word "contusions," which has a long "u," not a short. This makes it sound like he says, "concussions."
Elmer identifies the fish he catches as a "red-striped barracuda". Red barracuda are found in the Eastern Pacific only.
Daffy tends to the duckling without checking for then removing any buckshot.