On Mon, 21 Dec 2015 20:47:56 -0700, Tony Hwang
wrote:

Micky wrote:
On Mon, 21 Dec 2015 19:02:56 -0700, Tony Hwang
wrote:

Micky wrote:
On Tue, 22 Dec 2015 00:04:23 -0000 (UTC), "M. Stradbury"
wrote:

Is it true (or an urban myth) that a swimmer would be sucked
under (presumably to drown) when a capital ship sinks?

In panic, someone might not hold his breath, and even more likely, he
might not take a big enough breath to be able to hold his breath for
long, but I would think if one does get a big breath and doesn't
panic, he should be able to hold it easily long enough to come to the
surface again.

Does it depend on how fat he is how fast he surfaces? Probably. So
if you anticipate being on a sinking ship, try to gain weight first.
(When my brother was in Viet Nam during the war, my mother wanted him
to gain weight to tide him over if he was taken prisoner. He didnt'
go on patrol and he wasn't a flier, so the odds were very slim he
would be taken prisoner, but other than that, I think she was right. )

I would think so. I was in a 6-man rubber raft that went over a
small falls and under water and though I wasn't tied to the raft, I
went under water too. How much more so with a big ship.

Something about traveling and being on my own made me fearless however
and I confidently waited, with my eyes open iirc, until I popped up
again a few seconds later. Without the raft.

This was the Dranze River in France, just east of Geneva, Switzerland.

Basic fluid mechanics.

You know that the swirl direction of opposite of
Southern hemisphere. CCW and CW. Rotating earth.

So I've heard.

Hmm. This post is not in reply to my reply to you where I took issue
with the importance of swirling. But I'll answer anyhow.

I'm not doubting that water in toilets swirls, or that water in eddies
swirls. I'm saying that swirling water has nothing to do with
sucking someone in behind a sinking ship.

In fact the water probably isn't swirling. The forces that make water
swirl, in a bathtub for example, are weak compared to the tremendous
amount of water that surrounds a large sinking ship. If the ship
were not sinking, there would be no swirling, and I don't think
sinking an inch every minute is enough to permit or cause swirling.
m
It's when the weight of the ship and the water it now contains is
greater than the weight of the water the whole ship displaces that
sinking quickly begins, and at that point there isn't time enough
before the ship has totally sunk for substantial swirling to begin.
Perhaps not any swirling at all. Note that it takes quite some time
to have it begin even in a bathtub.

The stage of sinking slowly can take hours, but when sinking quickly
begins, it takes no more than a minute, maybe two.

To beat this to death, I think the thousands of times people get to
watch water go down a sink drain overhwhelms their lack of experience
with sinking ships. However one can drop or throw rocks in a lake or
a river pool, off a pier for example, and see that there is no
swirling.

(One could even attach small balls that float to the rock, with some
weak "adhesive" that fails when wet, and time how long it takes the
balls to return the surface. Varying the depth of the water, or
the release time of the "glue", one could measure three data points
and extrapolate to a ship and a person, and a person with a life vest.

(Or maybe one doesn't need the rock for all of these experiements.
While the water falling into the opening would slow down resurfacing,
that water has filled in the hole within a measurable number of
seconds, and the real question is, What is the acceleration of a human
of given weight and size due to buoyancy, and how long would it take
to stop downward travel and cause upward travel, and what would the
total time be? All but the downward speed could be extrapolated just
from measurements made by releasing floating balls from an underwater
device.)

Hey, couple months ago whale watching boat rolled and sank hit by a big
wave West of Vancouver Island, few died and some survived. A couple

I heard abou tthat.

survived is from Calgary here. They both said they got sucked under and
then surfaced. My 2nd uncle is life time Navy man, Captain(ret), ROKN.
He said same thing.

I didn't hear about that. Good to know. Should make OP happy to
know too.

Just remember to pretend you're in the doctor's office, suck in a big
breath and hold it.