I've been to the Atlantic when I visited both North Carolina (Cape Hatteras) as a teen and South Carolina (Hilton head) in my early 20s. My brother also used to live in Virginia Beach so I've been there a few times...
I visited California for the first time this past summer and saw the Pacific for the first time. We first saw it outside Los Angelesat Manhattan Beach and it wasn't much to see. There was lots of seaweed in the water and it was just grayish looking.
BUT, a few days later we headed south to San Diego and Mission Beach and it was AMAZING!! The water was so clean, nothing growing in it. You could see your feet even in 10 - 15 feet of water, as well as the sandy bottom. We loved it!! The waves were huge and swimming was so much fun. Until your eyes started burning from the salt....

I would love to see Souraya respond to this...she's probably seen every body of water known to man!

And KBlaix, Lake Ontario is my backyard! I grew up in Syracuse, NY about 30 minutes from the lake and went to school in Oswego, right on the lake! My favorite body of water in the WORLD, is the St. Lawrence River!! Spent all my summers there and hope to have a vacation spot there someday...