As the guy (or woman or chick or boy or girl, dunno) above me showed, there's a load of em. Sir Francis Drake is the most famous - but he was more a privateer. He helped defeat the Spanish Armada and was close to Elizabeth. He also circumnavigated the world, I'm pretty sure, which was huge back then.
Then there was John Davis who helped map out the Americas, most famously the Falkland Islands, which stayed in English control for centuries, even to this day.
I know there are other famous ones ( like one who explored the sea around Canada to look for a non-existent northwest passage up there - can't remember his name), but can't remember em right now - sorry.
the person above me was way more thorough.