Needs review
Source: Stormwrack

Description: You can attack in the middle of a fast pass by your opponent.

Prerequisites: Swim speed

When swimming, you can take a move action and another standard action (such as an attack) at any point during the move. You cannot take a second move action during a round when you make a swim-by attack.

Normal

Without this feat, you take a standard action either before or after your move, but not in the middle of your move.