the aquarius barrier system used at middleton beach is composed of heavy duty marine ropes with a nylon plastic strut design. the vertical struts are made from solid nylon plastic that is sufficiently rigid that marine life can't become caught in it; small creatures pass through it, larger ones are blocked without being trapped. the horizontal ropes give the structure strength in the water. the barrier has a horizontal breaking strength and has an expected lifespan of around 10 years.