Damage does not seem to calculate consistently (or, sometimes, at all) when a land unit is attacking a naval unit right on the coast and vice-versa. Here is a screenshot from a game where I am Germany and am at war with Sweden, who is an active player:
His 1 unit is moving away from my 7 on the shoreline, and no damage has been sustained by either party for over a day. This has also happened with an AI in another game. My submarine was sent ahead to scout out troop movements, and had erroneously disembarked, leading to a confrontation with the AI's main stack as said stack was embarking. No damage has been done to either party in the three days they have been fighting. Here is a screenshot of that one:
His 1 unit is moving away from my 7 on the shoreline, and no damage has been sustained by either party for over a day. This has also happened with an AI in another game. My submarine was sent ahead to scout out troop movements, and had erroneously disembarked, leading to a confrontation with the AI's main stack as said stack was embarking. No damage has been done to either party in the three days they have been fighting. Here is a screenshot of that one: