There still seem a lot of leaps of faith here. Thomas forgot his father's name (or maybe William was William John Moody), and then the birth at sea wasn't registered (which would explain the lack of any credible candidates so far for Thomas's birth record), when I am wondering why he would be born at sea anyway. Do I need to look for a family migration somewhere, but then there is a brother Samuel who is born after him in 1857 in Goole anyway? Some parts of the story fit, but others don't. And for a man born in a ship, his actual shipping record to NZ seems to be missing too, and it seems easy enough to find most of those records around that time (he is the only one in my family I haven't found relatively quickly).
I remain confused, although also feeling that this fit with William Moody and Sarah Markham looks closer to credible than anything so far.