Plus they prevent water from hindering your vision by allowing it to run off as soon as it hits.
It's just like playing any other sport-your goals are to protect your eyes without hindering your vision.
If you are stuck on a level and it is hindering your enjoyment of the game, then use a walkthrough only for that purpose.
This type of frame provides the benefits of structure without hindering balance or range of motion.
Behavior is based on self-interest and motivated by who can help children get what they want or who is hindering that process.