The decaying SAFER FSO tanker contains an estimated 1.1 million barrels of oil and has been moored and maintenance-free near the Yemeni port of Ras Isa for several years, according to the United Nations.
The tanker has been stranded since 2015 and could be extremely dangerous.
"Since the engines were not running, the inert gases pumped into the storage tanks to prevent the accumulation of explosive gases from the stored oil were not replenished, which is why there are worried about a catastrophic explosion." said Doug Weir, research and policy director of the British Conflict and Environment Observatory, to CNN.
The obsolete tanker had been converted to a floating storage platform before the Yemen war.
The cargo stuck aboard the ship could be worth more than $ 60 million based on current oil prices.
According to Houthi-led news agency Al-Masirah, the Houthi government has previously called for safeguards from UN that it would be able to sell oil extracted from the ship, which is currently impossible due to international sanctions.
Lowcock said that, depending on the season and water flow, an overflow of the tanker could reach from Bab el Mandeb to the Suez Canal and possibly to the Strait of Hormuz.
Kristina Sgueglia of CNN contributed to this report.