make a cartesian diving squid in a bottle

Get a fishing lure squid, bonus! Most of them glow in the dark, they are really easy to find!

Get yourself an eyedropper, this one was glass I'm sure a plastic one would work, you just may have to add a weight or something to the bottom

pull the squid over top of the eyedropper, it may take a lot of wiggling, as the rubber eyedropper tip is a lot wider than the squid head, I found it easier to oil the squid and turn it inside out, rolling it onto the eyedropper, being sure to wash it before you put it into the water.

Squeeze the bulb of the eyedropper and get about enough water to fill just the bulb, this may take some trial and error, to get enough water that his head just comes above the surface

This is what it should look like to be neutrally buoyant, prepare for awesome. (the term neutrally buoyant brought to you by my dive instructor Neil, and the letter E, for Ed, Ed owns the dive shop, Ed and Neil are good peeps.

fill the water to the very top of the bottle and put the lid on TIGHT. Squeeze the bottle and play with your new diving squid friend! He's even awesome at night, I contemplated giving it to my daughter to play with as a night time toy, but was reminded by my much wiser (and older) husband that it probably wasn't a well thought out idea, as she is 2.5 years old.

**OH! I originally did this with a 2L pop bottle (yes, pop, I'm Canadian) but it was really hard to make him dive, so I swapped it to a 500ml bottle and that fixed the problem

So obviously the 'science' in this is buoyancy and density, if it really boggles your mind you can read more about traditional cartesian divers here: http://en.wikipedia.org/wiki/Cartesian_diver yeah yeah it's a wiki link but it seems to have all the right info. 

Go, be with squid, be with bliss