Step 1:

    Start by sketching an arc/semi circle shape like in sample 1 below.  Then start to add triangular shapes for the fins and tail like in sample 2.

    Step 2:

    Once you have your general guide down you can start to add detail like below.

    Step 3:

    Once you’re happy with your dolphin lightly erase all unwanted marks and go over it again using a darker pencil or fine line pen like in sample 5.  Once this is done your ready for the fun part, shading!

    Step 4:

    I haven’t it shown it here but for extra effect try adding a few splashes of pencil marks below the dolphin.  This will give the impression that its jumping out of water.