Water is a really good conductor of sound so I would have to say that it would be to send the message underwater because a more dense medium produces a louder sound
A series circuit means that there is only one current. Which means that everything is sharing that one wire. Homes are normally wired with a parallel circuit, which means that there is more than one current running through the house. If you have a series, if you turn on one thing for example a light switch, than everything will turn on with it. But of you have a parallel you can turn on everything one by one, and save energy.
Trust me. I just took my semester test in physical science this morning, and I passed. This is exactly what we learned. <span />