At Loe Pool a barrier dammed the ria of the River Cober causing the formation of Cornwall's largest lake. Very little of the Loe Bar shingle is locally derived (compared with nearby Gunwalloe beach material to the south) and the deposits have been tentatively dated as Eocene. The composition of the bar deposits are: chalk flint 86%, quartz 9%, grit 2.6%, greensand chert 2% and serpentine 0.5%. The shingle coming from drowned terraces of the former river that flowed down the English Channel; the nearest onshore source is away in East Devon. Longshore drift is unlikely to have caused the formation because the bar is situated between two headlands but it plays an important part in the maintenance of the bar, with a strong current flowing to the south-east from Porthleven to Gunwalloe, depositing shingle along the bar. The ebb flow is not a simple reverse flow and is not strong enough to remove all the deposits. * Marine Conservation Zone The Mounts Bay Marine Conservation Zone (MCZ) was designated on 29 January 2016 and covers an area of Mount's Bay south of the coast from Long Rock to Cudden Point. The site includes the sea around St Michael's Mount and tidal reefs such as the Greeb, near Perranuthnoe, and the Long Rock. The MCZ protects habitats ranging from exposed high-energy rock on the coast to sand and muddy sand on the sea floor. The seagrass beds, Zostera marina, mainly grow in the sub-tidal zone and are important as a nursery area for fish and shellfish, as well as a feeding area for birds. Damage from the anchors and chains from moored boats can damage the beds. Animals within the zone include stalked jellyfish such as Lucernariopsis campanulata and Lucernariopsis cruxmelitensis, and a fish the giant goby (Gobius cobitis). On 19 August 2018, a white harbour porpoise was seen near Mount's Bay. History Spanish attack A Spanish raid took place over two days in August 1595 during the Anglo-Spanish war of 1585–1604. It was conducted by a Spanish naval squadron led by Carlos de Amésquita on patrol from Brittany. They landed, sacked and burned Newlyn, Mousehole, Penzance and Paul. A militia force led by Francis Godolphin was unable to drive the Spanish away. Pirate attacks In August 1625 "Turks took out of the church of Munigesca in Mount's Bay about sixty men, women and children and carried them away captives".