I have several types of free-floating vegetation to pick from:

  • Trees

  • Reeds/grasses

  • Lily Pad like-plants

Which type would best survive in the open ocean supporting small pockets of creatures, since they would be faced with winds, waves, and other dangers?

Edit: I want these plants to float at the surface of the water and be home to non-aquatic or at least only semi-aquatic creatures.

  • $\begingroup$ Freshwater floating island ate quite common: en.m.wikipedia.org/wiki/Floating_island maybe one can drift into a large lake, or low-salt sea like Baltic. I believe there are some trees or bushes that can live in salty water; getting them into a floating island is a stretch, but not a very large one. $\endgroup$ – Bald Bear Dec 29 '18 at 5:12
  • $\begingroup$ its actually fairly big stretch, there are no plants that can survive in the open ocean, you are better off starting with one of the algaes that evolved in the ocean, like kelp or sargassum. You might be able to exploit pumice rafts to start. $\endgroup$ – John Dec 29 '18 at 5:35
  • $\begingroup$ To be clear do you want this from earth life? $\endgroup$ – John Dec 29 '18 at 5:39
  • $\begingroup$ Yes, I do. @John $\endgroup$ – Thalassan Dec 30 '18 at 3:51
  • $\begingroup$ @Thalassan Something slightly related you might be interested in: worldbuilding.stackexchange.com/questions/128647/… $\endgroup$ – Fay Suggers Dec 30 '18 at 13:36

If you are looking for free floating sea vegetation, go for the Sargassum

Sargassum is a genus of brown (class Phaeophyceae) macroalgae (seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral reefs, and the genus is widely known for its planktonic (free-floating) species.

Most species within the class Phaeophyceae are predominantly cold-water organisms that benefit from nutrients upwelling, but the genus Sargassum appears to be an exception. Any number of the normally benthic species may take on a planktonic, often pelagic existence after being removed from reefs during rough weather; however, two species (S. natans and S. fluitans) have become holopelagic—reproducing vegetatively and never attaching to the seafloor during their lifecycles. The Atlantic Ocean's Sargasso Sea was named after the algae, as it hosts a large amount of Sargassum.

They are also known for supporting micro-habitats:

Large, pelagic mats of Sargassum in the Sargasso Sea act as one of the only habitats available for ecosystem development; this is because the Sargasso Sea lacks any land boundaries. The Sargassum patches act as a refuge for many species in different parts of their development, but also as a permanent residence for endemic species that can only be found living on and within the Sargassum

EDIT After the OP mentioned the plants have to float above water

Example of floating vegetation islands are found around the world. For example, in Italy there is the lake of Posta Fibreno (referencing the Italian page since the English one doesn't report the same content) hosts for centuries an island made by peat and small vegetation growing on it, with roots directly dangling in the water.

However, open ocean has the problem of the lack of fresh water, therefore you need to adapt using plants which can fare well using sea water, like mangroves.

  • $\begingroup$ I just realized i skipped over the floating above the water part, i hate posting from a mobile! $\endgroup$ – Thalassan Dec 29 '18 at 4:57
  • $\begingroup$ @Thalassan, added that part $\endgroup$ – L.Dutch Dec 29 '18 at 5:08
  • $\begingroup$ The problem with floating above the water is there is no real advantage to floating above the water in the ocean, what you need is something like forest progression where sargassum is slowly replaced by by a different type of bigger spherical sargassum that sticks above the water to compete for sunlight. Storm action will keep breaking up the clumps so you never get a complete replacement. $\endgroup$ – John Dec 29 '18 at 5:31

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