The arrows were sprayed as directional aids for a series of races.
This morning ERA enforcement officers and the Police made the responsible party prove that the markings and signs made were removable by water.
The organisation has been instructed to remove all signs by Friday night, and it seems to be co-operating.
Environment and Resources Authority (ERA) officers together with the Police Force will ensure the complete removal of the signs.
Further action will be considered if the signs are not removed within the stipulated timeframes.
ERA reiterated that organised activities within protected areas under the Environment Protection Act may require a prior permit from the Authority. Organisers are encouraged to consult with ERA to determine whether a permit for their activity is required.