Holland built the first practical sub, but in the U.S. civil war at least 3 subs were made . Hunley, Pioneer ( by same team of experts ) and one other called the St John’s after where it was found by unknown people . This was only 10 -15 years earlier than when Holland submitted the plans . None of the subs were very effective and were built by acknowledged experts so NAvy was not as stupid as it sounds. Batteries , electric motors and engines.needed to be developed in 1875 that were not there then developed enough for use.