The Air Hogs Thunder Trax R/C tank to boat converting toy is very cool. It drives on just about any terrain including sand, snow, grass, gravel, mud & water and does a very good job doing it. One of the coolest features is the transition from land toy to water toy. With the push of a button, it converts from a tank-style toy to a boat.
It is specifically built to handle rugged environments so tall-ish grass, rocks, gravel shouldn't be an issue.
It's easy to operate and is a ton of fun for your kiddos (and even your adults).
The minor downside is that it may take some time for it to convert back from a boat to a tank but it can still be used on land even when in boat mode. Once it dries, it shouldn't be an issue.
Overall, we give it a 4.95 out of 5 stars, which by our standards means we must really love it!