I watched a special on this battle and was surprised at the fact that Mark Antony lost this battle so easily. One reason (conflicting accounts here) The show saidthat he had massive desertions, while the Wikipedia article sites malaria. So he was undermanned either way. also his ships were not as agile as Octavians. Strange these two thought after fighting civil war that they could co-exist as rulers. They should of saw this coming.It makes you wonder how much influence Cleopatra had on Mark Antony.
Egypt was the granary of the Roman Empire so if Antony and Cleopatra wanted to extort or blackmail Rome, they could do it by cutting off the supply of grain and starving Roman citizens. Octavian understood the power Antony had, and he also harbored enmity with Cleopatra for her seductions of Julius Caesar so when Antony took up with her, he crossed a line that Octavian could not accept. Antony's allegience became divided because Octavian knew that Cleopatra was not loyal to Rome, unless she had a hand in ruling it. Octavian and the Roman Senate would not suffer Egyptian hegemony within the empire, and since Antony refused to leave Cleopatra, the civil war had to be fought. So yes, Cleopatra's influence was quite strong and beguiling.