First, you have to consider that you wouldn't be 'together' until the remaining spouse died. The one left behind would have to go on with life. In doing so, there is no guarantee that the surviving spouse wouldn't remarry. In that case, final wishes may change.
If it bothers you that much, perhaps you could find a comfortable compromise. Ask your husband if he'd consider cremation, so that you could take some of his ashes to be interred (buried) in a cemetery or mausoleum so that you could be put next to him, and have a place to go when you wanted to feel close to him. That way, you could be next to him at your death. And, if you were to remarry, there would be a space on the other side of you for your new spouse as well. With cremation, he could still be buried at sea, and you could still be together' after death.
Also, you could put a few of his ashes in one of those tiny glass vials that you wear on a chain. That way, you could have him 'with' you forever.
My husband was married before we met. His wife became ill and died. She was buried in their family cemetery, with a double headstone. So, when he dies, I am to place him next to her. There is no room for me on the other side, as someone already owns that plot. We discussed this prior to getting married, and agreed that he would be next his first wife. I will be buried in the cemetery with my own family. The point is, it doesn't really matter after death if you are together or not. You won't know either way, and it is better to know that you did one final thing for him that made him happy. I would much rather know that I did what he wanted in life than worry about being with him after death.
Also, you can have a few of his ashes put in a glass vial that you could wear on a chain so that you could have him 'with' you forever.