Some porpoise behaviour

Here's a link to some footage of porpoises I filmed near the Mew Stone off Skomer Island last summer: http://youtu.be/xC_Bho_DEBY  Sadly the definition is not so good but the great thing is that it shows whats happening on the surface but also some of what is happening below the surface ...
Seeing the porps under water, it's clear to see how quickly they can manouver and change direction. It shows just how tricky it is or even impossible to count porpoise numbers with any real accuracy from just surface sightings.  One animal may surface and then seem to resurface again when in fact as we can see from the film it is a completely different animal. The first one shoots off surfacing randomly elsewhere whilst others seem to appear from nowhere. I was amazed at how fast they can suddenly accellerate and swerve, flashing their flanks as if rounding up or disorientating their prey. I am not sure if in this case its a "team effort" but I do have some film of a single animal doing so on its own with a fish escaping its jaws by a split second. We will try and add this to the diary later.