JON GAMBRELLLAGOS, Nigeria (AP) â¿¿ The powerful waves of the Atlantic Ocean crash against rusting hulks beached along the coastline just outside of Nigeria's largest city, as lines of cargo ships waiting to come to port stretch across the western horizon. Government officials say they don't know how many abandoned ships choke Nigeria's waterways, but they cause tremendous environmental and navigational hazards. And as more wash ashore daily, the massive vessels cause fast-moving erosion along Nigeria's beaches that can tear away a kilometer of shoreline in a matter of days, experts say. "Shorelines are supposed to seasonally increase and decrease," said Ikenna C. Onyema, a professor of marine sciences at the University of Lagos. "When a manmade structure comes in between, it cuts out its life." Forgotten ships rust across Nigeria's roughly 850-kilometer (525-mile) coastline, while others can been seen partially submerged on inland waterways and creeks. Some have been there for decades, while others only days. Many, abandoned after the lucrative theft of crude oil, serve as hulking metaphors for the lawlessness that plagues Nigeria. The history of abandoned ships in Nigeria is intertwined with the slowly growing, strangling grip of corruption that nation has faced since it gained its independence from Britain in 1960. The first such ships came amid the booming trade of importing cement into the country during the massive projects of former military ruler Gen. Yakubu "Jack" Gowon in the early 1970s. Ships backed up for miles with cement, awaiting for up to a year trying to come into the country. Only later did officials acknowledge much of the cement was inferior and companies put their ships in line to collect fees for being kept waiting. Some of the cement hardened in ships' holds, sinking the vessels. Today, it appears many of the boats left to rust along the coast belong to the increasingly lucrative industry known locally as "bunkering" â¿¿ stealing the crude oil pumped out of Nigeria's oil-rich southern delta by foreign companies. The CEO of Royal Dutch Shell PLC, the dominant firm in Nigeria, has estimated that thieves steal about 150,000 barrels of oil a day from the region by drilling or sawing into pipelines to install their own spigots.