An Uneven Keel (слэш)

Keel: the backbone of a ship’s hull – damage to which can cause listing, an inability to remain upright.
Severus Snape has spent the three-odd years since the end of the war recovering and squaring his debts, both financial and spiritual. Now he's finally down to the last thing he needs to do before he can move on. The one last selfish thing he wants. Unfortunately, Harry Potter has never been very good at cooperating with other people's plans.