According to our best available source - the historical account by Herodotos of Halikarnassos, written some 40 years after the event - this is indeed what happened. The army and fleet were sent to two adjacent bottlenecks and fought to prevent each other getting outflanked. Both battles continued over the span of the same 3 days. The naval battle ended in a stalemate, but when it became known that the land army had been defeated, the Greek ships withdrew.