Defy Danger or Golden Opportunity

In Dungeon World, if the GM describes a hazard and a player disregards it should that trigger the Defy Danger move or be considered a Golden Opportunity that triggers a GM move?

For example:

GM: The swamp beast lurches out of the mist, a mass of grasping, strangling tentacles reaching out to towards anything within reach. What do you do?

Fighter: I run up and hit it with my sword.

Surely that isn’t a simple Hack & Slash. But should it trigger a GM move or a Defy Danger move?

Would it change the answer if the Swamp Beast had the Reach tag but the Fighter’s sword only had the Close tag?