This is not a cruise ship but the regular ferry that runs between Oban and Lismore Island. It is one of their small ferry boats that only carry a few cars and a handful of passengers.
For a bargain of £4.25 you get some stunning scenery and a trip across Oban bay and back, and almost two ROUGH hours at sea. When the ferry gets to Lismore, just stay on if you're intending to come straight back.
As it is a small boat, it is quite a rough ride when the sea is not calm. Keep this in mind if your prone to seasickness. However, if you're pushed for time and haven't much money, this is the cheapest option. I would recommend this if it's all you can do. There are no facilities, though an indoor cabin with seating area is provided.
If you want more comfort, the sail to Mull is £6.45 return (foot passenger). The much larger ferry has outdoor decks, indoor observation lounges, a reasonably priced bar, cafe, shop, etc, and it is a lot smoother. You still get the lovely views.