Swimming flags

In Australia, New Zealand, Philippines, and the United Kingdom a pair of red/yellow flags is used to mark the limits of the bathing area on a beach, usually guarded by surf lifesavers. If the beach is closed, the poles of the flags are crossed. The flags are colored with a red triangle and a yellow triangle making a rectangular flag, or a red rectangle over a yellow rectangle. On many Australian beaches there is a slight variation with beach condition signalling. A red flag signifies a closed beach (or, in the UK, some other danger), yellow signifies strong current or difficult swimming conditions, and green represents a beach safe for general swimming. Blue flags may also be used away from the yellow-red lifesaver area to designate a zone for surfboarding and other small, non-motorised watercraft.

Reasons for closing the beach include:

no lifeguards in attendance
waves too strong
dangerous rip
sharks
tsunami

A surf flag exists, divided into four quadrants. The top left and bottom right quadrants are black, and the remaining area is white.

Signal flag "India" (a black circle on a yellow square) is frequently used to denote a "blackball" zone where surfboards cannot be used but other water activities are permitted.