SHEIKH IJLEEN, Gaza Strip, Nov 5 (Reuters) - Away from Gaza's troubled reality and beyond its polluted shore, Shorouq and Sabah Abu Ghanem surf in a world of their own.

The two girls, 13 and 12, learned how to swim at the age of three at the hand of their lifeguard father.

They can swim up to 10 km (6 miles), dive to seven meters (25 feet) and surf on plastic boards that they hope one day to trade in for competition-grade models.

In the sea I find my freedom. I feel free of everything I leave behind on land, said 13-year-old Shorouq.

Gaza is under blockade. We lack surfboards, we lack diving gear. We lack many things. But out in the sea it doesn't matter.

During this year's heatwave the shallow waters off the beach were no escape to Gaza residents. It is polluted in several spots because of insufficient sanitation and a crippled sewage treatment plant.

But the daughters of Rajab Abu Ghanim swim confidently out to the clean waves beyond the shoreline.

My girls are like sea beasts. They are excellent swimmers and surfers, says the father of seven, who has been surfing for 15 years and has won prizes in long-distant swimming events.

The Mediterranean waves are fickle and often modest, and surfing has never been a popular sport here.

But in 2007, Dorian Doc Paskowitz, a Jewish surfing legend, brought 15 surfboards to Gaza after he saw film of two Palestinians practicing on a shared, makeshift board.

Those boards quickly disappeared among the young men of Gaza's Beach Refugee Camp and the girls never got a chance to try them.

Gaza Palestinians on the beach or at open-air restaurants by the seaside are surprised to see the two girls and their female cousins Kholoud and Rawand paddling out into the surf.

Some people tell us we could drown, but we tell them they know nothing about us, said 12-year-old Sabah. When they watch us paddle right out of sight, they change their minds.

Many Palestinian women in conservative Gaza, which is under the control of the Islamist movement, Hamas, are accustomed to bathe clothed, and find it offensive for girls to go surfing.

They don't deter us, Shorouq said.

(Reporting by Nidal al-Mughrabi)