De Mok I was built in 1939 at the Rijkwerf (Royal Dutch Navy Yard) located in Willemsoord near Den Helder. The vessel entered service on 1 April 1940. It was designed to achieve a speed of 12 knots and operated with a crew of 18. The armament consisted of one 50mm cannon and two 12.7mm (0.5 inch) machine guns.

On 14 May 1940, De Mok I departed from Terschelling for England and was subsequently employed in the Evacuation of Dunkirk. According to Winser’s account, the vessel completed two trips during the evacuation, transporting 100 troops to Dover at 17:30 on 31 May and an additional 114 troops at 18:00 on 1 June. During a later mission to Dunkirk, De Mok I sustained heavy damage and was beached. Following repairs, the vessel was commissioned into service with the German Navy.

After World War II, De Mok I was recovered, returned to Willemsoord, and repaired. In 1949, the vessel underwent a complete refit to serve as a training ship for young recruits of the Dutch Royal Navy. It was renamed H.M. RC II, then redesignated Y 807 in 1950, and finally renamed Hendrik Karssen in 1954. At that time, the armament was updated to include two 20mm machine guns.

The vessel’s namesake, Hendrik Karssen, was a 24-year-old naval serviceman from Semarang and a survivor of the Battle of the Java Sea. He was captured by Japanese forces during the war and was executed after defiantly spitting in the face of a Japanese officer and proclaiming "Long live the Queen." He was posthumously awarded the Bronze Lion for his bravery.

De Mok I was reportedly decommissioned in 1973. Subsequently, the vessel was refitted to accommodate 30 passengers for overnight stays and was believed to have operated carrying up to 67 passengers on day and week trips in the Wadden Sea and the North Sea.

As of April 2018, no further information regarding the vessel’s history or current status has been documented.