Surfing Life — Issue 337 2017

Open any textbook on

oceanography and it will

tell you that waves start to

break in water that is 1.3

times as deep as the wave is

tall. This is the mathematical

depth where swells will ‘spill’

over as they find shallower

water. Waves like Shipsterns,

however, don’t subscribe to

textbook definitions. Instead,

it contorts swells into an

obstacle course, creating

ledges and giant steps that

have come to define the place,

and the lunacy that goes with

riding it.

“The step at Shipsterns is

caused by dramatic changes in

the depth of the ocean floor,” says

local charger Marti Paradisis. “It

starts off super-deep off the back

of the reef. Then the ledge out

the back makes the wave stand

up and start to fold on take-off. It

then wraps onto the next (even

shallower) platform, which is the

step, or end section.”

Specifically, it’s this abrupt

transition from a shallow rock

shelf to an even shallower

platform that creates the step. As

the concentrated energy of the

breaking wave gets forced onto

the shallower patch of rock ledge,

it causes the wave to effectively

trip over itself, throwing up

The

Shipsterns

Bluff,

Tasmania

those mutant steps. Just how

pronounced the step is, often

comes down to the swell period.

We all know swell period

measures the energy of waves.

The higher the period or energy,

the more a wave’s going to feel

the bottom contours. The easiest

way to think of it is like this:

period represents how deep a

wave’s energy stretches under

water, and the higher the period,

the deeper this energy goes.

“It’s all to do with water

drawing off the reef,” explains

Marti. “Longer period swells draw

more water, therefore the bottom

which makes the step is shallower

• causing it to break (more
  intensely). No matter how short
  the period, there will generally
  always be ‘steppy’ waves on some
  sets at Shipsterns. Most of the
  time finding the good ones is pure
  luck of the draw... but if it’s a
  solid swell and 20-second period,
  you know it’s gonna be mutant.
  Almost unrideable.”
  Which begs the question:
  just how much more mutant can
  Shipsterns go?
  “I think we’ve seen it at its
  ugliest,” reckons Marti. “The
  crazy thing is, you can be there
  on those days for hours on end,
  and then out of the blue, one will
  break perfectly and leave you
  awestruck.”

Step

Case Study:

p