If this is for an anchor rode you should not be using a swivel.
You do have a number of mechanical errors in the splice itself.
For a standard splice the tucks are always "under one, over one". I see a number of places where you are "under one over two". The strand that you are 'weaving' should always pass under one strand and then over only one strand. You also have some other funky stuff going on, but I can't quite make out from the picture what else is happening (without being able to rotate the line and trace the strands).
As a technicality, you also have a lot more tucks than are needed . I bet Polypro doesn't need more than five tucks at most.