STT Tower Controller reported a tall-masted sailboat was in unsafe proximity to approach end of landing runway resulting in a go-around and a critical ground conflict. Controller also reported failed enforcement of vessels to remain clear of runway.

Narrative

At XA10z; Aircraft X; was issued a go-around by the STT local controller due to a sailboat crossing closely to the approach end of Runway 10. The sailboat was potentially in an unsafe proximity to the arriving aircraft. Aircraft X was approximately 1 mile final at time of issuance and did over fly the vessel but wasn't in conflict with any aircraft. The normal procedure for sailboats in that area is for the vessel to navigate west around bouys stationed outside the Runway critical area. Aircraft X was re-sequenced with ZSU and landed safely at STT. No separation was lost during this event and no aircraft were overflown. High mast boats however; continue to be a potential hazard to airport operations. There needs to be enforcement of maritime activities at the end of the runway. There continues to be incidents where aircraft are too close to the masts of sailing vessels. There are a bunch of mariners down here that are not experienced with the area and the restricted zone at the end of the runway. I would recommend signage on the breakwater on each side of runway to steer clear of the restricted area for high mast boats. All it takes is the mast to hit a wing to down an aircraft.