a) Device placed in/on the ship ahead of time, or
b) Waterborne attack, i.e. suicide boat / drone, USS Cole style
Almost certainly *NOT* a mine. Torpedo unlikely.
Remember the game "Minesweeper?" Imagine a grid with millions of squares. Not enough mines in the entire Iranian inventory to cover even a fraction of the GOO.
Damage appears to be amidships, starboard side.... Which is the most likely place a "suicide boat" or waterborne drone would aim for.