Final answer:
The Germans used U-boats, or submarines, to bypass the British naval blockade during World War I, which effectively cut off supplies to Britain and her allies.
Step-by-step explanation:
The new weapon that the Germans used to get around the British naval blockade during World War I was U-boats (Submarines). The Germans had developed effective submarines and torpedoes to counter the British-led naval blockade. By declaring the waters around Great Britain a war zone and using U-boat attacks, they sought to cut off supplies to Britain and her allies.
Despite restrictions such as the agreement to limit submarine warfare following the sinking of the Sussex, German submarines continued to play a crucial role in naval combat during the war. These U-boats attacked without warning, which violated international law and contributed to the United States entering the war after incidents like the sinking of the RMS Lusitania.