While any ship's Master is free to use any signal he may consider appropriate, this signal you refer to is very commonly used to convey the most urgent of messages: "Abandon ship!". Upon hearing this, you would proceed to your assigned station (normally by a lifeboat).
This signal is made mainly for the benefit of those who may be in the open deck, and cannot hear the same signal being rang by the general alarm (a system of bells found inside accommodation and enclosed work spaces).
Continuous soundng of a ship's whistle is a distress signal. If you only heard one or two blasts the ship could be signalling as required under the rules of the road.
6 short blasts means man overboard.
A boat is using astern propulsion and is in the act of backing up.
"I am about to turn to starboard".
three short blast
It means a vessel is going to back up.
Two short horn blast from a vessel means that she is turning port and one short horn blast that she is turning starboard
One short blast of a boats horn can mean a couple of things.Horns are used to communicate with other boats to avoid collisions.If you are overtaking a boat from the rear, one short blast will let the other boat know that you are going to pass them on the starboard side, two blasts indicate passing on the port side. The other boat should return your one blast, or two blasts, to let you know that they are aware of you and acknowledge your intentions.If you are heading straight towards another vessel, one blast will indicate you intentions of passing port to port. If you pass starboard to starboard then two blasts are required. The last situation is if you are going to be crossing in front of another boat. Remember, the boat coming from the right has the right of way. Giving one blast lets the boat to your right know that you see them and are going to give way to them, again all these signals should be acknowledged by the other vessel. If you do not receive a return signal, assume they are either drunk or do not see you. These rules are for inland waters, such as lakes rivers, bays, harbors and the like. Different rules may apply when you are on the high seas.One short blast of a boat horn means that the boat is altering course in a starboard direction. One long blast means that the boat is nearing a bend and cannot see oncoming boats.
A boat is astern propulsion and is in the act of backing up
Three short blasts means you are operating in reverse. One prolonged blast followed by 3 short blasts means boat under tow in redcued visibility conditions.
One short blast of a horn mean while boating may mean a couple of things depending on where you are. Some of the meanings of the short blast include request for drawbridge to open, intention to pass of the left side and intention to change course to starboard among others.
You could 'toot' your horn...
Toot
toot