That's a bit of a puzzler, if reading commentaries is any guide. Quite a few of them note that the sea was a place of chaos and danger in Jewish imagery. I'll take their word for it. This ties the "no longer any sea" together with verse 4: "'He will wipe every tear from their eyes. There will be no more death' or mourning or crying or pain, for the old order of things has passed away."
That's plausible: "Dear God, be good to me; the sea is so wide, and my boat is so small." Breton fishermen's prayer.
And yet some people love the sea. I love to sit by the ocean and watch the waves come in; others love to surf, or swim, or sail, or dive.
Maybe it ties in with verses 22-23 instead: "I did not see a temple in the city, because the Lord God Almighty and the Lamb are its temple. The city does not need the sun or the moon to shine on it, for the glory of God gives it light, and the Lamb is its lamp." Maybe there's no more sea because what we love in the ocean is available even better in something else.
It seems that in sailing we make the grand chaoses of water and wind serve us; similarly with surfing or swimming--we finess otherwise unhelpful forces for our own use and pleasure.
Divers see hidden things, and visit with creatures we don't meet with otherwise.
And me? The powerful waves crashing up and down the beach combine rhythm and variation--perhaps they're a kind of music.
We're warned that trying to imagine heaven is futile, but maybe there's something(s) that fulfill what we distantly find in the ocean now.
I know, the Beatific Vision fulfills them all. But the orthodox claim is that the resurrected have bodies, and presumably do things with them. So, unless the passage is simply symbolic, we can ask "What is it we love in the ocean, and where else might we find that?"