Review (5/5): Accept no substitute
Ok, I'll admit to a bit of bias since I am from the same place where Doc Martin's is made, but after many years of living under the Hawaiian sun and spending several hours each day working outside and/or playing in the ocean, I absolutely swear by this stuff. I put about a dime-size squeeze on my face and ears before a long surf or paddle session and it does the job for hours without wearing off. The "6-hour protection" claim is definitely legit. Plus, it doesn't give you a "whiteface" that is hard to wash off like some of the other, more well-known, more expansive brands like Vertra. Doc Martin's seems to wash off fine at the end of the day, and doesn't leave me with clogged pores like some of the cheaper face protectants.
Also, it is a great value if used on just on the face and ears - a tube will last me a couple or three months w/ daily usage. If you use for the entire body you might run through a tube pretty quick, but hey - it's a small price to pay to protect your skin from the ravages of the sun!
Doc Martin's is a fantastic product, I swear by it and so do several of my friends.