An electric hydrofoil surfboard has the capability of carrying a 200-lb surfer at 25 mph for 25 miles. See the video here.
Let’s say the mission is to plant 500-lb mines near an enemy’s harbor entrance.* The video above shows a 200-lb payload being transported 25 miles. Obviously, the electric hydrofoil surfboard would have to more than doubled in size to carry a 500-lb mine. It would need more battery power to go from 25 miles to 100 miles. But this should be easy to design. Let’s assume this can be done and that 500 mines could be put at the entrance to the enemy’s harbor. Let’s assume that 200 mines sink or damage ships. The cost of the electric surfboard is $12,000. For the upgraded design, the cost might be $100,000. To place 500 mines would cost $50 million. But what would be the cost of 200 ships]—and the uncertainty of the enemy in entering or leaving the harbor? It would probably be a worthwhile effort. Other ways of emplacing mines are by aircraft and submarine. This method would be much less risky. Imagine losing one plane or one submarine. What would that loss be just in terms of dollars?
What would be required? First, the size of the surfboard would have to made larger to support a 500-lb mine. I would estimate the size of the 500-lb mine as 7 feet long by 1.5 feet in diameter. This would require a larger electric motor. It would require more batteries. Control of the hydrofoil delivered mine would have to be autonomous. It would have to use control surfaces vs. the weight shifting by a human surfer. This is just design work. It should not be too difficult. Once the mine reached its destination at the harbor entrance, it would have to be designed to sink to the proper depth (e.g., five feet below the surface) and the surfboard/hydrofoil would be discarded.
One of the areas that would need to be researched is up to what sea state could the electric hydrofoil operate. Since most invasions are going to be done in mild sea states, this probably will not be a problem.
*What I have is to counter an invasion of Taiwan by Communist China by placing mines at the entrances to the four primary harbors opposite Taiwan. The suitably sized electric surfboard operating autonomously could transport the mine across the 100 miles of the Taiwan Strait. Of course, this would be after the invasion commenced.
