BARDSEY ISLAND, situated two miles from the end of the Lleyn Peninsular is a voluntary marine reserve and is listed to be a site of special scientific interest.  Underwater visibility extends to 20 metres on ocasions and sea life is rich in variety.  Drift diving on the Western side will find a rocky terrain with sea-urchins and crawfish during the right months.  Currents can be fierce and slack water occurs in the sound at approximately 2.25 hours after low water for the area.  CASWENAN is an isolated rock bearing 210 degrees magnetic, distance 1 mile, from the lighthouse.  Caswenan rises from approximately 44 metres to 22 metress and should only be dived on neap L.W. slack - approximately 1.5 hours after low water Bardsey local L.W. time.

Positions of the two wrecks are (Ref: Chris Holden - DGPS) 'Ilesha', a twin engined motor vessel at 52 45.095'N 004 47.260'W and an unknown well broken and dispersed sailing vessel known as the 'Horse Brass Wreck' at 52 45.815'N 004 46.785'W.