We had a fantastic time with Wave Expeditions. We took the Balsa River Class II & III tour, which was roughly 13 km and two hours long. (See my full trip report here.)
The guides were really fun but still put safety first. We were given instructions on the bus and then we practiced following all the commands once we got in the raft. Once we got going down the river, it was non-stop excitement. It was much wilder than I expected for class II & III but that just made it more fun. Our guide Warner knew every rock, branch, twist and turn in the river and expertly guided us through it all. (At lunch we found out from one of the other guides that Warner is actually the owner and founder of the company so we really lucked out!)
Aside from a fun (and safe) voyage down the river, Wave Expeditions provided a lot of extras. We stopped part way through for water and a fresh fruit picnic, which was much needed on a hot day. Additionally, they are the only outfitter that has a private exit area from the river that offers showers and changing rooms. And you will find very few half-day tours that offer lunch, let alone a homemade traditional Costa Rican lunch with a bonus sugar cane demonstration and moonshine tasting.
And the photographs… wow. These are a steal at $30. I had no idea they had taken so many photos, and the quality was really amazing. The photographer did such a great job of capturing the fun, excitement, and action of the day.
I highly recommend Wave Expeditions for a great day out on the river. Whitewater rafting was not necessarily the activity I was looking forward to the most in Costa Rica, but I think it turned out to be the most fun day of our trip. It was an absolute blast.