Built in 1939 on the Rijkwerf (Royal Dutch Navy Yard) at Willemsoord near Den Helder.

De Mok I entered service on 1st April 1940. Her designed speed was 12 knots, with a crew of 18. She was armed with one 50mm cannon and two 12.7mm (0.5ins) machine guns.

She left Terschelling on May 14th for England and was put to work for the Evacuation of Dunkirk.

(Winser’s book notes that she did two trips, bringing back 100 troops to Dover at 1730 on 31st May and a further 114 to Dover at 1800 on 1st June).

On a further trip to Dunkirk she was heavily damaged and beached there. She was repaired and put into service with the German Navy.

After the war she was found, brought back to Willemsoord and repaired. In 1949 she was completely refitted as a training vessel for young people entering the Dutch Royal Navy and renamed H.M. RC II, then in 1950 Y 807, and in 1954 Hendrik Karssen. At that time, she was armed with 2 x 20mm. machine guns.

Hendrik Karssen was a 24 year-old Navy man from Semarang and a survivor of the Battle of the Java Sea but in Japanese captivity. He spat in the face of a Japanese Officer. He called out "Long live the Queen" as he was bayoneted to death without a blindfold. He was decorated posthumously with the Bronze Lion.

De Mok I was apparently bought out of service in 1973. Since then she was refitted to sleep 30 and was believed to be earning a living carrying up to 67 people for day and week trips on the Wadden Zee and out into the North Sea.

As of April 2018, no further information concerning this historic vessel has been received. We would invite persons with knowledge of her history and whereabouts to contact the Association.