The Sharks (20-21) got on the board first in the sixth when Chris Walker led off the inning with a single. It was the first hit for the Riversharks on the evening off Dan Reicher (3-1).
Lloyd Turner followed Walker with a single of his own, and Walker scored on a double play off the bat of Marquez Smith. Smith drove in Scott Knazek in the eighth to double the Sharks lead.
The lone Blue Crabs (21-20) run came in the bottom of the eighth when David Espinosa hit a solo home run off Mariano Gomez.
The Sharks added an insurance run in the ninth on a sacrifice fly from Jake Eigsti, scoring Drew Macias. John Lujan pitched a perfect ninth, including a pair of strikeouts, to pick up his league-leading ninth save of the season.