Factors that effect sound waves in water?

[Josh03]

1. For this question, I need to explain why sound waves emitted into ocean water sometimes fail to give accurate results.
2.I have thought about, the salt density and the waves traveling through different water temperatures, but need to expand on these two ideas and don't understand it enough to do so. If anyone could explain these ideas a little more, I would be very grateful.

 

[NascentOxygen]

I think regions of differing densities might deflect the sound (refraction) off course. You might have a layer of fresher or warmer water, or a channel of such where it emerges from under the sea, or a river emptying into the ocean. Just guessing.