Ocean biomes contain wide expanses of water, which could have islands scattered throughout. It is not uncommon for caves and ravines to exist beneath the surface. It is also possible for part of an ocean to freeze over, if it borders a snowy biome, like the taiga or ice plains.
In the Update Aquatic, oceans gained a variety of variants such as the cold ocean, the lukewarm ocean, and the warm ocean.
The lukewarm ocean is one of the types of ocean biomes that has teal water color, kelp, seagrass, and sand at the ocean floor. All ocean mobs spawn here. Underwater ruins that generate here are made up of sand related blocks. A deep lukewarm ocean variant also exists.
The cold ocean has a dark indigo color added to the water. Though the floor is mostly gravel, there is a few patches of sand and dirt along with sea grass and kelp. All ocean mobs (except for the tropical fish and pufferfish) spawn here. A deep cold ocean variant also exists.
The frozen ocean variant has a dark purple color to the water, although much of the water is replaced by ice. This is the only place where icebergs can be found. Like other cold biomes, it snows here instead of raining. The only ocean mobs that can be found here are salmon, squids, and drowned. Frozen oceans will never generate near land, and always have a cold ocean surrounding them. A deep frozen ocean variant also exists.
A warm ocean has water that is a light green color. Sea grass is more generated here then any other ocean though there is no kelp. Coral reefs spawn here as well as sea pickles. All ocean mobs spawn here (excluding the cod). Like a frozen ocean, they will not generate touching land and will always be surrounded by a lukewarm ocean. A deep warm ocean variant also exists, though players must use customized Superflat worlds or Buffet Mode to get them. Coral reefs will also not spawn in deep warm oceans.
Oceans are possibly one of the most inhospitable places in the Overworld for players. Masked by the lack of most mobs, is the risk of drowning. A player can easily drown while attempting to dive deep under water without protection. They could also starve to death while trying to swim large distances across the ocean. In addition, a player may also be attacked by passing guardians or drowned. Trees are scarce in ocean biomes; even if a player happens to find an island, they are less likely to find wood, an essential ingredient in many survival tools.
A deep ocean is one of the worst places for an unsuspecting player to spawn, because of the depth of the water. A player could suffer or die from drowning damage if they do not consume a potion of water breathing, or have a respiration-enchanted helmet or turtle shell.
A boat is the best mode of transportation while traversing this harsh biome, since it increases a player's speed, saving them energy (thus slowing his/her hunger loss), and decreases the chance of getting attacked by guardians. A boat also allows the player to float, without having to use their jump ability.
Oceans are a good place for fishing, since there is nearly no risk of the fishing rod digging into any blocks while doing so. Fish are some of the main sources of sustenance, and crops can be grown on a hydroponic farm. Pufferfish can be gained easily by fishing in the ocean, and they are the ingredient required for potions of water breathing. Both normal and deep oceans are home to squids, making them a good hunting ground for ink sacs, as long as the player can dive down to grab them safely.
A player can isolate themselves nearly completely from monsters, as long as all surfaces are well lit. The remoteness can also provide isolation from other players.
If a player is aiming to dive underwater to gather sand or clay, or to raid an ocean monument, it would be wise to create potions of water breathing, and armor with the respiration, aqua affinity, or depth strider enchantments. These potions and enchantments will increase the time players can spend underwater, or help a player mine blocks faster underwater. If a player combines all of these with a potion of night vision, walking underwater is like walking on land.