In 1922 he began a secret attempt to salvage what was thought to be £2 million worth of gold coins (£100 million in 2012 prices) from the SS Tubantia, a ship which sank off the Dutch coast in 1916. When a rival salvage operation started the following year, Sippe won a landmark court case which ruled that, as his divers had found the ship and started work, he had the sole right to salvage it. In 1925, after £100,000 (£5.2 million in 2012 prices) had been spent on the salvage attempt, he concluded that though the cargo had been in the ship, the difficulty of accessing it made it too dangerous for divers to recover, and so the project was abandoned.
