In the very south of the Miura Peninusla is a tiny beach which draws a lively crowd on sunny days for barbeques, swimming and fishing. It's surprisingly easy to get to this little gem; just take the Keikyu line all the way to Misakiguchi at the very end, then catch the regular Keikyu bus to Aburatsubo and follow the people clutching their beer coolers and inflatables.
Araihama is well known as a great spot to see the majestic Fuji, especially Diamond Fuji, and it is also the home of Kamehameha, the popular Hawaiian beach hut.