swim cap / head covering

[yupito]

I don't have the fullest head of hair and would like something I could wear in the water to protect my noggin from the sun.

I have been using a lycra swimming cap from Nike with success. It does not have a strap, but the elastic is strong enough to hold the cap while you dive. Tyr also makes a swimming cap designed for triathlons that could work (http://www.tyr.com/shop/warmwear-cap-p-233.html).