Elmusk was one of many Marines being sent to Logue Town because of the rumors about the "Silver Eyes" performing some kind of test there. Unlike most of the other Marines on the ship he was stationed on, he had no interest in arresting the famous crew despite their high bounty, instead he was planning on going after "The Rovers of The West". Sure The Rovers were only a small crew with low bounties, but in West Blue they were known for attacking merchant ships and generally killing everyone on board.

Since he didn't have anything to until they arrived at the Polestar Island Elmusk decided to kill the time by practicing some  moves. Naturally he didn't actually use his spear since he didn't want to accidentally hurt someone, instead he used a staff the same size and weight.
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Zerry was simply waiting until the start of the meeting and in the meantime checking out the possible competition. It was of course hard to tell who was there for the test and who was just a regular tourist, but the Fishman didn't care. After all it was just something to kill the time with and he would find out soon enough either way.