I grew up in India, so the Arabian Sea and the Bay of Bengal were what we saw most often. At Kanyakumari, the Southern end of the Indian peninsula, I also saw the Indian Ocean merging with these two- it's a sight worth seeing.
The Ha Long Bay in Vietnam, and the Sea around Bali, the Sea visible from a plane in Japan, are some others. Singapore is also surrounded by Sea waters all around.
In the U.S., both Atlantic Ocean (at Myrtle Beach, Charleston, New York city), and the Pacific (at Los Angeles) were the ones I remember.
In Europe, whatever is visible in North France (Mt. St. Michael), as well as South France- Marseilles. I guess the Mediterranean and the Sea between Italy and Greece too- the Adriatic? Took a cruise/ferry from Brindisi to Patras and back. Also in Venice.
These are some prominent ones that I remember.
