Water is a weird and wonderful substance. Most liquids are made up of essentially separate molecules -- gasoline molecules, for instance, have little attraction for their neighbors, so each is pretty much independent. Water molecules, in contrast, have relatively strong attractions to their neighbors. If they didn't, water would be a gas, much the same as methane, ammonia, oxygen and carbon monoxide, all of which have about the same molecular weight. (The unusually tight linkage between individual molecules of water is due to "hydrogen bonding," the topic of a future column.)
Because of the tight bonding of water molecules, you can think of a glass of water not as trillions upon trillions of independent molecules, but as a single "supermolecule." Consider the water sitting in the pipe leading to your kitchen sink faucet. When you turn the faucet on, you're releasing one "tentacle" of a gigantic molecule of water that includes all the water in the network of distribution pipes linking your community. When a stranger on the far side of town opens her faucet, she releases another tentacle of the huge monster. If both of you simultaneously put your hands under the flow, you're connected to each other via the same "supermolecule."
If you live in Arcata, Eureka or Blue Lake, you get your drinking water from the Ruth Lake reservoir, created by the Matthews Dam on the Mad River. Although the dam cuts the reservoir off from the downstream river, they are inevitably linked. Sometimes it's obvious, such as when water flows in a continuous stream over the spillway (on the left in the photo); sometimes it's more subtle, since a trickle is always making its way under the dam through pores in the ground. Either way, it means that your tentacle is linked, not only to water waiting to flow from every faucet in town, but to the reservoir and the river and thence to the Pacific Ocean.
Earth's "seven seas" are, of course, really just one big ocean: there's no boundary where, for instance, the Pacific stops and the Atlantic starts. So when you put your hand in the flow from your faucet, you're physically linked through this single supermolecule of water with, for instance, a Yanomamo tribesman washing in a tributary of the Amazon 2,000 miles upstream of the Brazilian coast.
At which point the jingle "Reach out and touch someone" takes on a whole new meaning.