No dice are used; outcomes depend entirely on position and troop types.
Unpredictability comes from the limited moves and killing attacks per turn and the option to rout rather than die.
Though it is a deterministic game. I do not find it at all predictable.
No dice: fire is physical dexterity and melee is arithmetic.
The core rules use no randomiser apart from coin tosses for set-up and first move. Shooting outcomes come from the physical behaviour of toy projectiles; melee from comparing numbers. Dice appear only in an optional handicap and the appendix uses a coin toss for equal cavalry clashes.
Either the numbers taking part in the melee on each side are equal or unequal.
Strategic-level engagements are resolved without dice by the ratio of fighting values.
When forces stay within 2,000 yards (armored) or 4,000 yards (unarmored) for over an hour, the umpire may decide by relative fighting values from Table I. At 2:1 the inferior is removed; at 3:2 the inferior loses half and the superior is unharmed; at 4:3 the superior is crippled and must withdraw temporarily. Armored ships cannot be captured by unarmored ones regardless of numbers.
Two forces meeting, with odds of 2 to 1, the inferior will be removed from the game.