On the morning of December 1, 1875, Swatara was anchored in a harbor of Pará, Brazil, when the ship's dinghy capsized.
A strong tidal current swept the dinghy backwards from the side of the ship, where it had first capsized.
One of the dinghy's crew initially grabbed onto the small boat, but then lost his grip and began to sink.
Deneef jumped overboard from Swatara's gangway, swam to the drowning man, and dragged him back to the dinghy, where they were later picked up by a cutter.
Displaying gallant conduct, Deneef jumped overboard and rescued one of the crew of that vessel from drowning.