Silver Class Silver Class seats are the normal economy seats on Seajets. They are on the lower decks of the ships (if the boat has more than one level). They are airplane type seats but they have slightly more leg room than a plane and of course you can get up and go for a walk at any time.
You will be assigned a seat number with a letter and number but strict seating is normally only enforced when the ships are very full in July and August.
Club Class Club Class seats are one step up from economy (aka Silver class). These seats are normally on the higher deck or a separate area of the ship and offer slightly more spacious seating. Most people, however, cannot tell the difference and complain that an upgrade is not really worth the money.
Platinum Class Platinum Class is the top VIP class. It's equivalent to first class and if you want to splash the cash you will notice the difference over Club and Silver class seating. Here all chairs come with a table and there are electrical outlets for your convenience. There's a dedicated server for snacks and drinks (although you still have to pay for these).
The seating is larger and plush (normally arm-chair type seating) and normally the Platinum Class lounge is in a separate quite room. If you've been travelling prior to boarding your ferry, you may find these seats the perfect place for a snooze.