• Boundary rips are often created when longshore currents created by waves in the surf deflect off solid obstructions like groynes, breakwaters, rock outcrops and headlands.

• Boundary rip current bathing hazards are caused by a combination of the rip speed and the offshore extent of the rip flow.

• Boundary rip speed increases with wave height and wave angle. Wave angle was an increasingly important control of rip speed as wave height increased. Boundary rips became active when wave height exceeded 0.5 m.

• The spacing between multiple obstructions can control the strength of the longshore current and hence the deflected boundary rip. Rip speed is significantly reduced when spacing is less than 4 times the obstruction length.

• The boundary rip flow pattern is strongly affected by the length of the obstruction. The offshore extent (and proportion of rip exits) of the rip flow increases as the effective obstruction length increases (length in relation to surf zone width).

• Boundary rips are especially hazardous to bathers on low-energy beaches that only occasionally receive high waves. These beaches do not usually have beach rips and the boundary rip hazard is often intermittent. This can lead to an absence of lifeguard cover, lower rip experience amongst beach users and an element of surprise when rip flows are strong.

• Under medium wave conditions (larger than 0.5 m) with large wave angles (45˚), boundary rip flow speed can remain high >0.5 m/s) while the surf is still accessible to bathers, meaning exposure to rip currents and rip hazard are both high.