.... "took a running go" doesn't specifically mean to run quickly, and here could simply mean "started running" or "got a running start". However, "to take a running go at something" can mean to try and succeed by running at it: "He couldn't open the door, so he went back a few steps, took a running go at it and crashed through".
Either way, the phrase imbues the waves with a sense of intent wherein they start running towards the shore so they can throw themselves on the sand.
not a teacher
Student or Learner