This is something I have seen a few tourists to this area have trouble with, foreign and Japanese alike. From HonShiogama station, the maps indicate pathways that aren't as obvious at street level. Today, let me show you the way to Marine Gate, the port for ferries servicing Matsushima and the Urato Islands.
We'll start at HonShiogama Station on the Senseki Line, 320 yen and 30 minutes from Sendai station.
From here, take the Aqua Gate exit. That's right, we're walking under the giant fish.
By the way, this fish is meant to be the Maguro Tuna for which Shiogama is famous. More on that later. Once outside, you'll be greeted by a view like this, probably without actual arrows.
Turn left, walking towards AEON. This is the easiest way to get there without getting lost.
If you see this, you're going the right way. Keep going.
Once inside, walk part the check-out lanes. The elevator is located to the right between the check-out lanes and the exit. Press the button and go to the second level. Out of the elevator, take an immediate right down a white-walled hallway next to Sanki.
You'll exit directly onto the pedestrian pathway. Turn left and keep walking until you see Marine Gate.
You'll be on the second floor of Marine Gate when you come up to it, so go straight in past the Blair Marina restaurant. Elevators will be on the right.
Take the elevators down to the first floor, then turn right.
Go straight ahead. To the right, you'll find the desk where you can buy tickets for the ferry to Matsushima from a member of the staff. Tickets for the ferry for the Urato Islands can be purchased from a ticket machine to the left.
I strongly recommend checking the schedule before you plan your ferry trip, which is easier to do in person at Marine Gate than it is online. Ferries to the Urato islands are few and far between, as I said before, but if you want to go sightseeing out that way, you can get maps and schedules right next to the ticket machine.
There is a lot more to see and do at Marine Gate, including an observation deck on the fourth floor (the roof) which has a great view if you have a few minutes to spare. Also, if you're in the mood for a bite to eat before you take to the water, there are several restaurants in the building, including a few on the first floor. In the departure lounge, you'll find Le Port offering snacks, drinks, ice cream and beer. Just down the hall to the right is a nice little bread shop, perfect for a snack on the go. A soba shop shares seating space with the bread shop and features a dish with maguro (that special Shiogama tuna) wontons.
So the next time you're in the mood to see one of the three best views of Japan from a ferry, come out to Marine Gate and have a good time.