How to prove this sorting algorithm is correct with loop invariant(s)?

Hello- I wrote out this algorithm and I am trying to understand loop invariants- what would be the loop invariants for this one? And which one is the best to confirm it's correctness?

Code to sort a sequence in decreasing order:

static void Sort(int array[]) { int size = array.length; for (int i = 0; i < size - 1; i++) for (int j = i + 1; j < size; j++) if (array[j] > array[i]) { int buffer = array[j]; array[j] = array[i]; array[i] = buffer; }