What is the story? This is the story of a man being unexpectedly eaten by an enormous shark, obviously.
What information is conveyed in each frame?
Frame one: small boat; man not expecting to be eaten by a shark (no evidence of guns or other protection); man relaxed - having a fag; calm water. We see the man's face so we can make an impression of him and care (or not) when he is eaten by the shark.
Frame two: enter the gigantic shark. The water is still calm implying the man is unaware - he is looking in the other direction. We are reminded that the boat is small by the aerial view.
Frame three: this was designed to highlight the horror of the man's last moments - we are placed just behind his recognisable red ball cap (very subtle, aren't I?) as the shark approaches. The speed of the attack is emphasised by the sudden cut from the aerial view in frame two.
Frame four: some general chaos and splashing around to make this seem slightly more plausible than if the shark just stealthily stuck its head over the boat side and scoffed the man. Again re-emphasis on the contrast in size between boat/man and shark - a sledgehammer metaphor for how helpless humans are against nature (especially impossibly large sharks). The red cap is there so the man almost certainly has not escaped (although it probably should have been eaten too).
Frame five: all is completely calm again. The shark has moved on and all that remains are the eerie signs of the presence of the man - the upturned boat (maybe should have had a big bite mark down one side?), the cap (which is actually getting on my nerves now) and the rod - leaving the possible interpretation that this is a lesson: if you go hunting (fishing), prepare to be hunted...
What information is necessary to understand the story? I think I have covered the key elements. We may wonder how far the man was from land, how deep the water is, how the shark got to be so bloody big, why the hat survived and the boat is undamaged but none of these things are essential to the basic story.
What essential information has been left out and/or what is included unnecessarily? Not entirely sure frame four is necessary but it may seem a bit too dramatic a change in tempo without it.