Some statistics (forgive the redundancy):
Radius - 5,400 mi or 8,690.458 km
Diameter - 10,800 mi or 17,380.915 km
Circumference - 33,929.2 mi or 54,603.754 km
Mass - 7.33x10^24 kg or approximately 1.23x earths
Density - 2,672 kg/m^3 or approximately 0.484% (half) that of earth
Surface Gravity - 6.478 m/s^2
Escape Velocity - 10.61 km/s or 23,736 mph
I am attempting to make a relatively plausible ocean planet with which to inhabit with many different oceanic creatures. My main concern is that it would be very difficult to do in the way I desire (using the statistics listed), despite my trying to apply all of the intricacies of physics and planetary science I can understand to attempt to alleviate the skepticism one might have with my proposed planet.
I have yet to clarify the solar system it will reside in and its location within said system as I'm aware it could drastically change the viability of my planet. It is left open for any elaboration to help me create this world. I don't mind about where in the system it formed or how it could form, where it resides or orbits from, what type of star it orbits, if it has neighbors or moons or whatnot, or anything else really, just as long as those things are established in such a way that allows it to have life.
This planet will be somewhat larger and more massive than earth, with less density (nearly half as much as earth) and slightly less surface gravity/escape velocity. It will be made up mostly of water and covered by a very deep global surface ocean which extends several dozen km downward (preferably at least 54km) or until exotic ice begins to form, as depending on various planetary factors such as atmospheric pressure and density the exact depth of exotic ice formation can vary.
Most ocean planets we know of are covered in ice shells, however I do not wish for my planet to have one. There could perhaps be a relatively small ice belt/ring around the equator if possible, as polar regions would experience more heating from oceanic forces (without considering rotation and other factors). However, this is not a must have if it isn't feasible, as the ices depth would probably be relatively paltry compared to the depth of the planets ocean(s) if such a belt was present at all.
Less gravity will most likely require a denser atmosphere and/or a lower atmospheric temperature in order to maintain said atmosphere, with water vapor retention being a key factor. Thus the presence of and strength of the magnetosphere is important. This atmosphere must retain the ocean's water vapor and also supply the necessary conditions required to support life in the ocean below (oxygen among others). It could potentially be very violent and stormy at the surface of the water but so long as life can exist below the surface I don't particularly mind.
I am aware that rocky/metallic core planets are typically more dense and usually maintain stronger magnetospheres, whereas my larger and less dense planet could potentially lack as strong of a magnetosphere. So my planet could have a relatively smaller rocky/metallic core (whose actual size and overall composition I am unsure of as of yet) surrounded/sheathed by a mantle made of exotic ice(s), whose interactions with one another I surmise could create and maintain a magnetosphere.
The transportation/recycling of nutrients upwards from the mantle/core to the deep oceans (to sustain life) I presume is possible in such a scenario. Downwelling is also necessary to recycle these nutrients from the atmosphere downward to the deep oceans. This could be caused by atmospheric conditions and wind/ocean currents in the water to allow for the replenishment of oxygen and other stuff from the atmosphere to the deeper depths below. There will be a need for a strong ocean heat transport system and an active atmosphere with wind and storms (caused by thick and/or dense atmospheric conditions) as well strong global ocean currents and oceanic density variations (caused by temperature gradients and salinity).
Overall planet size, density, gravity, planet composition (one big concern), and atmospheric/oceanic pressure/composition (another big concern) are all key factors in the development of life and gigantic ocean and deep ocean lifeforms, as well as for humans to be able to explore and traverse the planet in special-built submarines and dive suits/scuba gear (technological feasibility not withstanding).
I have done extensive research on many topics related to these necessary features and have yet to come up with all of the details necessary to satisfy my desire to have a somewhat realistic/theoretically plausible world
So for starters...
Are the basic values I have given in the beginning at all plausible for an ocean planet hosting life?
If you guys could help me in understanding all of the fundamental/crucial aspects of my planet, things I haven't thought of or considered, factors that I mention that simply won't work under any circumstances, or anything else I must consider/alter to create a viable planet, it would be much appreciated.
I am aware that there are others who are more educated on these topics than me and despite my passion for world building and science I am starting to feel out of my depth here (pun intended). I hope to learn from you guys so that I can make my world more realistic and plausible.
I am willing to make some adjustments to the figures already stated if absolutely necessary but I'd like to try and stick to the general parameters listed already. I will consider all suggestions given to me.