This was adapted by the Royal Navy for anti-submarine defence in approaches to harbours and ports by laying drift nets and snagging enemy submarines.

[1] In January 1917 the Royal Navy ordered 100 drifters from Canadian shipyards as part of a building programme in Canada.

[2][4] The main differences between them and their British-built counterparts were electric lighting instead of acetylene gas, a steam windlass instead of a capstan and the gun was further forward.

The drift nets provided for use in anti-submarine warfare were 120 by 20 yards (110 by 18 m) and required large wharf areas to perform repairs and maintenance.

[7] The drifters, though constructed in Canada, belonged to the Admiralty and were intended for use in British waters during World War I.

Canada had not been informed prior to this and had been sending crews to the United Kingdom in preparation for the vessels' arrival.

[48] Further difficulties arose when more training would be required as the drifter-type fishing vessel was not used in Canadian waters, and there was a lack of knowledge of the technology in Canada.

[1] By October 1917, the Admiralty changed its position, requiring 50 drifters to be sent to British waters, with the remainder set aside for Canada.

Further inexperience among Canadian builders in the construction of boilers and engines led to 42 of the former and 47 of the latter being built in the United States.

[50] Though the vessels were poorly finished and the crews inexperienced, the drifters performed their task of deterring U-boats from convoy targets.