Most sunscreens sold today contain harmful chemicals (like oxybenzone) or microparticles. Many do not protect against both UVA and UVB rays and end up preventing sunburn but not skin cancer. It is difficult as an individual to research the right product.
Luckily the Environmental Working Group has a "Guide to Safe Sunscreens" website we can use:
It has a searchable index of safe sunscreens, a list of characteristics to avoid ( http://www.ewg.org/2014sunscreen/what-not-to-bring-on-vacation/ ), tips on sun safety, etc.
I use "Kiss My Face" SPF30 sunscreen - it lasts well, is fairly sweat-proof, is all natural and does not contain oxybenzone, microparticles, useless additives like Vitamin A, etc.
While the guide seems to be focused on products available in the USA, I expect many of them are also available worldwide. And the EWG recommendations can form the basis for people in other countries evaluating the sunscreen products available in their home country.