A sound is a narrow passage of water connecting two seas or a sea with a lake. For example the Sound of Mull runs between the mainland peninsula of Ardnamurchan and the Scottish Island of Mull. The other tem in use for such a body of water is 'strait' as in the Straits of Gibraltar or the Singapore Strait a 30 mile by 10 mile strip of water separating the island of Singapore from Indonesia. The use of different terms does not seem to be influenced by geography. For example, in the UK we have the Menai Straits between mainland Wales and Anglesey as well as the aforementioned Sound of Mull and the Plymouth Sound. Both straits and sounds are notorious for having dangerous currents. The phrase 'being in dire straits' meaning finding yourself in serious trouble is linked to the nautical use of the term straits. A "sounding" is a measurement of water depth.