The earliest recorded appearance of this simple name form was in 1337, when it was called "La Loo",[1] but is mentioned as 'the lake' in 1302;[2] Situated between Porthleven and Gunwalloe and downstream of Helston, it is separated from Mount's Bay by the shingle bank of Loe Bar.

[9] The most likely origin is a barrier beach, (formed by wave action rather than by tides) that gradually moved onshore, as the sea level rose during the Holocene.

[10] The shingle coming from drowned terraces of the former river that flowed down the English Channel (the nearest onshore source is 120 miles away in East Devon).

[6] The deposits have been tentatively dated as Eocene[11] and compared with Gunwalloe beach material, very little of the Loe Bar shingle is locally derived.

Leland who visited the west country in 1542, reported that the bar was breached once in 3–4 years by storms causing sea water to mix with fresh in the pool, but it soon reinstated.

[16] Daniel Defoe in his tour around Great Britain writes that the River Cober 'makes a tolerable good harbour and several ships are loaded with tin', [between Lowertown and Helston, but not to the sea]; although over one hundred years before Defoe, Richard Carew (1602) described Loe Bar as "The shingle was relatively porous and fresh water could leave and seawater enter depending, on the relative heights of the pool and sea"[17][18] Defoe, writing in the early 18th century, appears to state that ships were then able to trade up the Cober to Helston; this would seem to be the origin of other documentary sources claiming a port for the town in the historic period.

[21] The 2013 investigations by the Camborne School of Mines project team,[22] show a chart of a cross-section of part of the valley between Loe Bar and Helston as being built up from a depth of twenty-five feet of silt, upon a belt seven feet deep of sea sand, above layers of peat from the remains of vegetation or of the ancient forest, that once covered Mount's Bay.

During storms the Bar can be overrun by the sea forming a series of washover fans resulting in, annual laminated sediments, which are unique in Great Britain.

[38] By 1908 it was becoming rarer and was last recorded here in 1915, its loss was believed to have been caused by a lack of fluctuating water levels following work to the adit (outflow from the lake).

Seed was grown in a greenhouse at Paignton Zoo, Devon by the Whitley Wildlife Conservation Trust (WWCT), and in May 2015 over 1,000 seedlings were planted on the east side of Loe Pool.

[41][42] Loe Bar is the only site in Britain where the subspecies leechi of the sandhill rustic (Luperina nickerlii) moth is found.

[46] A local legend states that the giant Tregeagle was doomed to remove the sand from Gunwalloe to Porthleven, from which the sea would return it.