Also anyone know if the concept of international waters was established at this time? Also, if it was and the Germans hit ships within the coastal waters of the UK wouldn't that violate the Geneva Convention which Germany had signed?
The Lusitania was a legitimate target of war, carrying ammunition and registered as an auxiliary military vessel of the Royal Navy. In effect, the British were using the passengers as human shields. That said, I don't believe it was so much a plot as unthinking, bureaucratic routine. Just business as usual, which in the new context of war suddenly had very different implications. Passenger vessels often carried military cargo, even in peacetime, and this was just a continuation. The more insidious part was the British instructions to civilian vessels to install hidden weapons and to ram U-boats if they followed cruiser rules, and the use of Q-ships to likewise punish U-boats for following the rules. If U-20 had approached the Lusitania with speakers warning the passengers to evacuate, it in all likelihood would have been rewarded by being rammed. Was it morally wrong to sink the Lusitania? Certainly, but an equal share of the blame goes to the people who irresponsibly blurred the line between civilian and military vessels, and knowingly or unknowingly used passengers as human shields.