1. Battle of HMS Prince of Wales & HMS Repulse against
Japanese airplanes on 10 December 1941; both the British battleship
and the battlecruiser were sunk. The first time in history that a
battleship succumbed to aircraft while at sea and fighting
back.
2. Battle of the Java Sea in February 1942; greatest clash of
cruisers in WWII.
3. Battle of the Coral Sea; history's first clash of aircraft
carriers.
4. Battle of Midway; history's first decisive clash of aircraft
carriers.
5. Battle of Savo Island; the US Navy's worst defeat "at sea" in
it's history.
6. Battle of Guadalcanal; nearly a dozen sea battles fought
around those islands: From Iron Bottom Sound, to Friday the 13th,
to Santa Cruz, to Tassafaronga.
7. Battle of the Atlantic; Germany's "Guerre de Course" (sinking
of merchant vessels) against allied shipping.