Kamogawa (鴨川), a resort city where you can enjoy the sea, hot spring, golf parks, etc., is very accessible by car across the Tokyo Bay Aqua Line. In particular, "Kamogawa Sea World (鴨川シーワールド)" is recommendable to visit as you can see not only normal exhibition but also various attractive shows by sea animals (see the below photos!).
Just in front of the sea, "Sansui Bettei (三水別邸)" , a Japanese-style ryokan locates, and we could spend a wonderful time there with in-house hot spring and delicious dishes using local seafood. Everything was tasty, but in particular, simmered alfonsino, grilled abalone and miso soup of Ise-lobster are must-eat dishes!! If you have time, walking along the seaside...visiting a temple of Nichiren named "Tanjyo-ji (誕生寺)"...are also soooo good!
Kamogawa Sea World (鴨川シーワールド) http://www.kamogawa-seaworld.jp/
Sansui Bettei (三水別邸) http://www.sansuihotel.com/special/