In a Storm of Swords it was mentioned that a ship (I don't remember whose) was pulled down by a kraken. Perhaps this Kraken is a servant of the drowned god who will fight alongside the iron born against the kind or the redwynes. Imagine how unstopable the Iron Fleet would be if the enemy ships were being pulled down from below the water.
Also I'm not sure that a women like Dany coming into power would be enough to upset the patriarchial ideas of Westeros. The laws do allow for women to rule if their is not a higher ranking male in line so it's not like they can't rule, although they are usually married soon after. We need to keep in mind that Westeros is a sexist society, look at how brienne was received as a night despite her skill at the joust and swordsmanship. Despite Dany's strength and that she will take the kingdom back she can't undo hundreds of years of prejudice.
Also I'm not sure that a women like Dany coming into power would be enough to upset the patriarchial ideas of Westeros. The laws do allow for women to rule if their is not a higher ranking male in line so it's not like they can't rule, although they are usually married soon after. We need to keep in mind that Westeros is a sexist society, look at how brienne was received as a night despite her skill at the joust and swordsmanship. Despite Dany's strength and that she will take the kingdom back she can't undo hundreds of years of prejudice.