<span>In order best to find out whether the obtained experimental results are worth mor etime and resources the group of scientists should present their results (could be done also in poster session) to other scientists in order to hear their opinion and get a feedback. The shoudl also ask another researchers to redo the experiments and to compare the results. </span>
The period of the wave would be halved
First we need to find the speed of the dolphin sound wave in the water. We can use the following relationship between frequency and wavelength of a wave:

where
v is the wave speed

its wavelength
f its frequency
Using

and

, we get

We know that the dolphin sound wave takes t=0.42 s to travel to the tuna and back to the dolphin. If we call L the distance between the tuna and the dolphin, the sound wave covers a distance of S=2 L in a time t=0.42 s, so we can write the basic relationship between space, time and velocity for a uniform motion as:

and since we know both v and t, we can find the distance L between the dolphin and the tuna:
<span>9000 Pascals
Looking on the internet, it appears that a human can only suck about 3 feet of water. So let's convert that measurement into a few more convenient units.
cmH2O = 36 * 2.54 = 91.44 cmH2O
cmHg = 91.44 * 0.73555912101486 = 67.26 mmHg
Pascal = 91.44 * 98.0665 = 8967 Pascals
PSI = 91.44 * 0.0142233 = 1.3 psi
Since we're dealing with science and the metric system is the most common system used in science, I'd recommend an answer of 9000 Pascals.</span>