Things happened quickly after Eren disappeared from his position.
Geer sensed that Eren was gunning for him. So he quickly raised his broadsword and placed it in front of him. The action was made just in time, enabling Geer to parry it effectively.
Swish. Bzzt. Boom.
Geer felt a tingle run through both his hands that were holding his broadsword when it clashed against Eren's axes. Eren deflected Geer's force all at once and made it swing above him as he ducked under the swing. He kicked Geer's hand that was holding the broadsword and directed the swing.
Using that kick, Eren controlled the swing's orientation, trajectory, and speed so that it confronted the incoming water slash.
The broadsword that had been coated in light blue flames at this point instantly evaporated the flying water slash launched by the lizard Wesen who was the team's tank and mid-range fighter.