The Luck property has no effect on fishing up White Pearls or MIBs from fished up Sea Serpents.
It may have some effect getting MIBs from Krakens or Leviathans from Fishing Nets, since it would be a part of its possible loot check (they are not guaranteed to have them, unlike the fished up MIB containing sea serpent script).
The luck property also has no effect on Treasure Chest loot, so it will not effect your chances of getting MIBs from them either.
Stayin Alive,
BG