passing on the port side from behind
It is the "Masters Salute", a salute to the Master of another vessel.
Runaway ship
2 short blasts
You need to transmit the Morse letter D (-..) with either a fog horn or hitting a bell every 2 minutes. Long blasts need to be 3 times as long as short blasts. The space between blasts is as long as the duration of a short blast. So the sequence goes like this: Blow the horn or hit the bell for 6 seconds, wait for 2, hit it for 2 seconds, wait for 2 seconds, and hit it again for 2 seconds.
2 short blasts
I intend to pass you on the starboard(right) side
you better get off that ship!!Two short blasts means that the vessel intends to leave you on it's starboard side. If you are in international waters it means " I am altering my course to port"
1 blast means, I am turning to starboard (right) 2 blasts means, I am turning to port (left) 3 blasts means, I am going astern (backwards) 5 blasts means, I don't know what you are doing, get out of my way.....and usually accompanied by colourful language and waving of arms etc. Often heard around the commercial jetty when recreational boats get in the way of large commercial ferries etc...
4 short blasts are the letter H is morse. On the River Clyde in Scotland a local bye law allows it to be signalled by a vessel going astern from a berth, generally a paddle steamer, indicating that it is going astern, it has difficulty in manoeuvring and warning other vessels to keep clear.
Patrol Torpedo Boat
They were the submarines of the German Navy. U-boat is short for undertseeboote (undersea boat).
Sailboat