Question

what new weapon caused the loss of life on boats, at one point targeting an american ship and resulting in the death of over 120 americans

Answer 1

FFS - the Lusitania was a BRITISH ship  caused the loss of life on boats, at one point targeting an american ship and resulting in the death of over 120 americans
hope this helps

Answer 2

In March, 1915, the U-Boot took down the RMS Lusitania. It is believed that, even though it was a supposed to be an innocent merchant boat, it could be carrying over 10 tons of weapon with it. 1195 lives were lost. Of those, 123 were north-american civilians.

The answer is The U-Boot