On 17 November 1912 the Wonga Shoal lighthouse was destroyed by the steel ship Dimsdale. The two lightkeepers Henry Franson and Charles McGowan were killed in the accident. The Wonga Shoal was a large sand bank off Semaphore: a lighthouse was stationed over it in 1901.

On the evening of 16 November 1912 the British ship Dimsdale sailed up Gulf St Vincent in ballast, seeking a cargo. Captain John Jones laid a course for the Wonga light and as he drew near ordered the course altered to keep the light on his port bow. However the ship was slow to respond to the helm and despite efforts to avert the accident the ship struck the lighthouse.

The lighthouse crashed into the sea and both lighthouse keepers were drowned. The Dimsdale's boats were lowered to render assistance but the keepers had been trapped in the wreckage with no hope of escape. Their bodies were recovered the next day. A court of inquiry found Captain Jones guilty of negligence and his license was suspended for 12 months. He was acquitted of the criminal offence of manslaughter. Dimsdale was barely damaged by the accident.

The destroyed lighthouse was replaced by a lightship temporarily, and later by a new steel structure. When the lighthouse at Marino Rocks was built in the early 1960s the Wonga Shoal Light was finally extinguished.

Parsons, Ronald. Southern passages: a maritime history of South Australia Netley, S. Aust.: Wakefield Press, 1986
Loney, J. K. Wrecks on the South Australian coast: including Kangaroo Island Yarram, Vic.: Lonestone Press, 1993

Cormack, Neil W. Sagas of steam and sail [Largs North, S. Aust.]: N.W. Cormack, 2002 (Yorketown, S. Aust.: Pioneer Printing Office) pp. 49-50