is one piece episode 337 filler?

Zoro is in the observation room of the Thousand Sunny. Looking out of the window, he sees something floating on the ocean and alerts the crew.

As the others look out, they see it's a barrel and Usopp notes it has the character for "treasure" written on it. They pull it out of the water.

Nami step outside and says it probably just has alcohol and food in it. She notes the whole message on the barrel says "Gift to the God of the Sea" and that this is a tradition for people to place those kinds of items in a barrel to pray for a safe journey.