The more I think, the more I'm having this hunch that a tidally-locked planet with an ice free ocean on the sunny side is impossible. I know that is not what you asked, but the question's Comment section is not enough to detail my questions.
It's unlikely that you can have the tidal-lock on your ocean-only low-density water on the sunny side - doesn't make sense to have the lowest altitude of the lighter side of the planet attracted more by the star. At best, you can handwave a heavy asteroid or a former moon that had a "low speed collision" with the planet so that it sorta-sunk-in-the-mantle-but-didn't-reach-the-core, so that the planet's mass-center is askew, but this is likely to require a good bulge of rock straight in the middle of your ocean.
Then, a tidally locked planet is unlikely to have an active core - if it had, then the viscous friction between a slow rotating tidal-locked crust and a fast rotating core will not last long enough for life evolution. With a dead core, a magnetosphere will be weak (or non-existent). Long term, the atmosphere long term will be gone blown away by the solar wind; except that I now realize that's not the worse thing to happen to the atmosphere...
... the "dark side" will gobble your atmosphere fast - at the temperatures of cosmic space, it will act as a cold-trap for the gasses in the atmosphere.
So, what gas is likely to freeze-solid on the dark-side first? I bet will be the water vapors. Now, either:
your ocean is small - then it will end with no-sunny-ocean-all-dark-side-ice fast; or
massive ocean - but then it will drive enough mass on the dark side, which will become heavier than the sunny side. A dead core makes the things even harder - there's no chance to distribute the weight by isostasy. Heavy-side farther than the lite-side is not a stable configuration, a tidally-locked body will minimize the potential energy turning their heavy side towards the attractor.
So... before getting to the "how's life on that planet", my question is "how do you explain the planet in the first place"?