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I was browsing a website with funny pictures and found this one quite interesting.

enter image description here

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    $\begingroup$ You need the surface tension to hold together the surface at the straw end. The surface is far too big in the other case for surface tension to have any significant effect. $\endgroup$ – Steeven Nov 10 '14 at 20:30
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Bigger problem than what is mentioned in the comments:

The picture shows a gap between the water and the side of the "swimming pool straw." (Can't even believe I just typed that.) Anyway, the straw trick only works because there's a pressure difference in the straw above the fluid, and outside the straw, above the fluid. The pressure below the fluid is at atmospheric pressure, 101 Kilopascals, and the pressure above the fluid is much lower (let's just call the inside a vacuum in which case the pressure is 0.) The pressure difference results in an upward force equal to gravity, which holds the fluid in static equilibrium. If the fluid did not form a tight seal with the container, or if there was a hole in the container, the pressures would equalize to atmospheric pressure both inside the straw and out. No pressure difference means no upward force, and your fluid accelerates down.

Even if your fluid did produce a tight seal you would 1) have issues with scaling because mass increases cubicly, but surface area only increases quadratically and 2) even ignoring that, you wouldn't be able to breathe in a super low pressure chamber as you swam.

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