What boarding a moving Bismarck at night would require

How long would Gurkhas take to capture Bismarck during the night action?

Reaching and boarding a moving ship would be the decisive difficulty; even with Royal Marines and sailors, the assault would remain dangerous and unpredictable.

The Gurkha-boarding counterfactual is chiefly a practical boat-handling and assault problem. The boats would have to get ahead of a moving Bismarck, approach together, and stay aligned long enough for troops to climb aboard. Linking them with a strong rope might let the ship's motion sweep the line alongside, though the attempt would remain extremely dangerous and uncertain. Gurkhas would probably need Royal Marines and sailors who understood shipboard movement, then fight through an unfamiliar vessel in darkness after the defenders realized what was happening. Boarding a large warship under way would be a complex joint operation even before combat began aboard the ship.