It is generally considered canon, unless contradicted in-game, in which case the game takes precedence.
A fishing explosive is a Slayer item used for luring mogres out of the water. Mogres are often killed for flippers, but can only be killed after a player has completed the Mogre miniquest. The explosives must be "used" on any of the three "Ominous Fishing Spots" on the peninsula of Mudskipper Point, located south of Port Sarim. Mudskipper Point can be quickly accessed by using a fairy ring code AIQ. The explosives can be bought from any Slayer Master.