I would simply confirm it ahead of time. I think they are on the web.
Aqua Ski is pretty well established. Thomas Horrell, Gator and Brannon Meek filmed there for Skurf's UP in the late 90s. But the operation has moved out to the Fortuna/Arenal area only in the past 4-5 years. Actually, I was surprised to find them there. I didn't know they had moved, and literally, I was hiking through the jungle on a trail around the volcano and I came upon a clearing and a shed with 2 MCs, hyperlite banners and a whole garage full of wakeboards out in the middle of nowhere in the jungle. That was unexpected, to say the least. Literally, I saw something odd through the jungle, and as I got closer and closer, it was looking more and more like a giant Hyperlite banner. Seemed kind of like a hallucination. But call ahead, because things like occasional earthquakes and volcanos can sometimes change business operations rather quickly in Costa. Anyway, Arenal has some AMAZING scenery, and all of Costa pretty much rocks anyway. Try to get into some surf while you are there.