The United States Navy SEa, Air and Land (SEAL) Teams, commonly known as Navy SEALs, are the U.S. Navy's principal special operations force and is a part of the Naval Special Warfare Command (NSWC) as well as the maritime component of the United States Special Operations Command (USSOCOM).
The unit's acronym ("SEAL") is derived from their capacity to operate at sea, in the air, and on land - but it is their ability to work underwater that separates SEALs from most other military units in the world. The experience gained from operating in the ocean and fresh water battle fields has shaped their identity and, as a result, they are regarded as being amongst the most highly skilled and trained amphibious units in the world. Navy SEALs are trained and have been deployed in a wide variety of missions, including direct action and special reconnaissance operations, unconventional warfare, foreign internal defense, hostage rescue, counter-terrorism, and other missions.
The Death of Osama bin Laden
On May 1 2011, a team of 20 Navy SEALs successfully completed the operation to kill or capture Osama Bin Laden in Abbottabad, Pakistan a city about 60 miles/100 kms from Islamabad, the capital of Pakistan. President Barrack Obama later confirmed the death of Bin Laden, but did not directly mention the involvement of Navy SEALs, saying only that a "small team" of Americans undertook the operation to bring down Bin Laden. 
That's one. OK, Where is al-Zawahari. You know, the Al.-Q. Mastermind? The Egyptian "Doctor" who never took (apparently) the Hippocratic Oath, which includes the phrase: "Above all else, do no harm." ?
Phil Plait has an interesting blogpost and his repliers words are worthy reading as well at Phil's weblog, Bad Astronomy, here.