Castle Peak is enclosed in the Tuen Mun typhoon shelter and usually has a very calm sea condition. Unlike many other beaches in the same district, its water quality has no correlation with tide level; no obvious deterioration in water quality may also be observed after heavy downpours. Instead, the beach may be potentially affected by local pollution sources from the typhoon shelter and the Tuen Mun fish market. Climatology in water quality at Castle Peak is the weakest among all six beaches in Tuen Mun district.

Monthly distribution of beach gradings at Castle Peak beach (2010-2014)