I know 18w15a changed where ocean biomes generate (i.e. "In newly generated chunks, you're less likely to find frozen ocean next to warm ocean") but I think something is off. Previously in the seed i'm using you could easily come across many different ocean biomes and now there is only ocean and deep ocean.

First Ocean and Deep Ocean with no temp qualifiers are back. They were replaced in 18w08a and should not be showing up at all in a newly generated seed.

"Oceans are now split into 5 temperatures: frozen, cold, normal, lukewarm, warm; Each ocean (except for warm) has a deep variant, like before; World generation should stay the same, but old chunks will only have normal oceans" https://minecraft.net/en-us/article/minecraft-snapshot-18w08a

Because of this no frozen or warm oceans are showing up. So there are no icebergs or coral and there is no change in the water color (except for swampland) because everything is the same ocean type (i.e. plain or deep). Ship wrecks and underwater ruins are in the same spots they were before, as are deep trenches with bubble columns, just the different oceans are missing.

seed: -8300275442758179407