Why if I put wireless access point near water(fish tank) will degrade its signal?

Question

I am reading this article: http://www.gnswireless.com/faq.htm

And for this question: What can I do if I am having wireless connection problems?

It says:

"Signal strength drop or fluctuation are common causes of RF interference. Change the channel on your access point or wireless router. Use only channels 1, 6 or 11 for non-overlapping channels. Change the location of your wireless products. Subtle changes (2-3 feet) can make a big difference. Do not put the access point or wireless router in a cabinet or enclosure. 2.4GHz phones, X-10, and Bluetooth devices will interfere with your wireless network. Change the location of the base for your phone, or downgrade to 900MHz phones, or upgrade to 5.8GHz phones. The wireless signal will degrade (or die completely) when going through brick (fireplace), metal (file cabinet), steel, lead, mirrors, water (fish tank), large appliances, glass, etc. If your wireless connection is only dropping during large file transfers or when a large number of wireless clients are connecting, change the preamble on all wireless devices to short."

But, what I really want to know is:

Why if I put wireless access point near water(fish tank) will degrade its signal?

Answer 1

Water can pose a lot of resistance for RF signals. Here's a technical document the explains this is great detail, which you might find interesting since it's relevant:

  Underwater Radio Communication, by Lloyd Butler VK5BR (1987)
  http://www.qsl.net/vk5br/UwaterComms.htm

These two quotes from that article address your question:

• "Water in its pure form is an insulator, but as found in its natural state, it contains dissolved salts and other matter which makes it a partial conductor. The higher its conductivity, the greater the the attenuation of radio signals which pass through it."

• "Attenuation of radio waves in water (and, in fact, in any conducting medium) increases both with increase in conductivity and increase in frequency."

Answer 2

If I recall correct from my college years. This happens because of two attributes of water.. First as it has mass it is a natural obstacle and so the RF cannot pass through it as if it was air. but the most interesting thing is that its reflective nature doesn't help the signal, because of its not still surface. This happens because lets say you send the following data packet "101010" not all values will reflect the same way so you might get "111000" and the protocol has to wait for the packet a second time and so on. (this is a true problem in long distance communication that's why we use differential antennas I think that this applies to WiFi RF too) I hope I helped.