Victory in the women’s 4x50m freestyle relay was not as straightforward for Marshall and her teammates, who had to fight back from eighth to take the title.
Laura Kinley gave the women another medal with second place in 50m breaststroke, finishing in a lifetime best of 31.3 seconds.
Meanwhile, the men toppled defending champions Guernsey in the 4x50m to take the final gold of the evening and set a Manx record.
Elsewhere, Mark Riley and Alan Wade won the island’s first gold of the day in the shooting in blustery conditions.
The pair scored a combined total of 183 to edge out Guernsey and Jersey by a single clay in the Automatic Ball Trap team competition.
Riley said afterwards that the weather may have helped as they were “used to shooting in windy conditions”.
In the tennis, there was no individual success but Laura Feely, Katie Harris and Karen Faragher claimed silver in the women’s team competition, and the men were third in their event.
Athlete Max Costley delivered another silver when he finished runner-up in the 3,000m steeplechase, bettering his bronze of two years ago.