To expand on Tim Prebble's comment, pumping a sine wave through the water causes the hose to move back and forth (well, actually in a kind of circular pattern, but that's not really important). Since the end of the hose is oscillating back and forth, the water makes a zig-zag pattern, similar to what happens if you wave a hose back and forth by hand.
In your scenario, is this person jumping into the water or just gradually sinking in?
If it's the former, consider the stages of what's happening to your character:
We hear above water ambiences as you establish that scene
There's a sharp crack as the body enters the water, while the ears are still above it
That initial crack blends into a more muted, ...
The piezos used in contact microphones pick physical vibrations from solid surfaces as you can see here, for example: http://vimeo.com/31926631
In that case of ice recording it makes sense to use those, but I don't think (and I hope someone correct me if I am wrong) a contact microphone under water -- in any other state than solid -- won't pick up much ...
As far as I'm aware, some hydrophones are actually made with contact mics (or piezo transducers) sealed inside a protective housing - so I think your logic is sound.
Actually, Jez Riley French makes some and it seems from his wording that that's how he makes his: http://hydrophones.blogspot.co.uk/2009/04/hydrophones-by-jrf.html
Seagulls always help sell the ocean.
What is important is what perspective you want to portray. Do you want intimate wave lappings on a lake shore? Or do you want large waves of an ocean as if you're standing on the beach? Or do you want distant waves as if you're standing in an alley near the ocean? I think your answer is a tad bit general because there is ...
guess I've found a good starting point for bubbling:
pink noise --> plugin called "Hysterisis" --> preset ASD_Juicer
pink noise --> plugin called "Molekular" --> preset Sheperd_Sortie
had to tweak stuff but those, for whoever is interested, is a good starting point for synthesized water bubbling
When you say "artificial soundscape" does this mean you can use anything BUT the sound of water? So, you couldn't record different kinds of running water sounds? Instead you would have to create that sound with an alternative source?
I suppose the question I would ask myself is "what does running water sound like?" I think that's a very loaded question. ...
You also could use a SM58 or any another microphone, put a condom over it, make a lot of gaffertape around it until it's dense and hold it in the water. (I would suggest to take your cheapest microphone :-).
A hydrophone is a specialized microphone for the use in the water. For example, if you drive thousands of miles to the north pole and want to record ...