Warship draft is set by harbours and canals, not a universal maximum

What is the deepest standard draft of a warship?

No exact record is given, but maximum practical draft depends on the harbours and canals the ship must use.

No definitive record holder is offered without further research. Draft is instead treated as a route and infrastructure constraint. A navy with deep harbours and no canal requirement can accept a deeper ship than one dependent on Suez, Panama, or shallow bases. The ship's intended operating geography must be traced before its draft can be compared meaningfully.