De Renquin served under Captain Callany. He discovered a Mermaid called Amfetriti whom he named Amy Ivans and took aboard the ship, hoping to sell her. He also capture her daughter and hid her in a wall compartment. In 1901, Callany was planning his retirement, at which point he told De Renquin he would hand over the ship to him. De Requin was poisoning Amy with small doses of mercury. De Requin arrested the Sixth Doctor on Callany's orders after the murder of Crawford. Later, De Requin freed the Doctor on Callany's orders, and had him and Peri Brown treat Amy Ivans.