Perito Moreno Glacier cruise is a must! It is only a short 30 minute to 1 hour trip, depeding what you choose, but it provides a great vantage point to the glacier. We just did the 30 minute tour and it was great. You can book a full day tour that includes the boat, or you can just book the day of at Perito Moreno. Make sure to book right away when you get to the parking lot, we did this and got on the boat right away, but some people had to wait an hour or so. Boat cruises leave every 15 minutes so you won't miss it. The cost is about $50usd