Identifying downstream and upstream V's of water is probably the simplest form of river reading. Downstream V's are that really nice tongue of water that is so much fun to ride over. Look beside this tongue and you will notice an eddy, a great place to catch a breath and look further downstream. Upstream V's occur when a rock/boulder splits a channel. We generally avoid these features or ride close to catch the eddy behind that rock.
The Downstream V
Downstream V Rapids are formed by water running over and around rocks and ledges. The most basic feature is the downstream V that develops when water runs between two rocks. This feature is also known as a tongue. Generally, this is what you want to aim for.
The Upstream V
The opposite of this feature is an upstream V. In an upstream V, water rushes around a rock. In the previous picture, you can clearly see two upstream V's. In general, we try to avoid upstream V's or at least lean into the rock to avoid capsizing.