There are numerous clips and videos on YouTube about swimming crawl. To make it easier for you, I picked out some clips you can watch that fit well thematically to the contents of the Freestyle Optimizer. Have fun with them!

Arm stroke Ian Thorpe -In the front view you can notice, where exactly the correct position to submerge the hand is supposed to be: In front of the shoulder which belongs to the hand.
Style analysis Alexander Popov – Alexander Popov is still considered to be the swimmer with the most beautiful crawl technique. In this analysis you will see why. There is a lot one can copy.
Style analysisMark Foster – A partly under water and slow motion video of profi swimmer Mark Foster.