A surface speed of 9 knots and a submerged speed of 4 knots? This thing is hilariously slow. At 4 Knots, you could almost walk faster to any comparably distant

A surface speed of 9 knots and a submerged speed of 4 knots? This thing is hilariously slow. At 4 Knots, you could almost walk faster to any comparably distant terrestrial destination. The impracticality is obvious: taking the yacht away from any one sea or port to another (something you'd presumably want to do after spending tens of millions on a superyacht), would mean traveling for an absurdly, abnormally long time inside a sealed, limited space with no easy way to leave mid-journey. At least normal surface yachts have reasonably decent top speeds of 20+ knots.