The information from this article is from the fan game or fan fiction and is therefore not canon.
The Sharkees are a race of half-merman, half-shark creatures living near Neptune's Kingdom (unofficial). They are lead by the King of the Sharkees. The Mer-people are at war with them. It is also known that these creatures are xenophobic and can't be reasoned with.
There are several sentries patrolling the dark waters. Graham can use the Trident to turn them into fish. Until he retrieves it, however, the guards can only be avoided.