How will the rising ocean affect aquatic life?
Biological communities (ecosystems) commonly change along topographic (bathymetric) slope - because conditions change along the slope. For example, there will be a temperature gradient with elevation along the side of a mountain, and gradients of temperature and the amount of incident sunlight reaching the sea floor just offshore. When climate changes, this can shift conditions up or down the slope.  

The organisms of an ecosystem must be able to colonize any "new habit" that may be created by climate change in order to take advantage of it.  If conditions shift too quickly for the species to adapt by migration along slope, species may become extinct before they can become established in another area. For example, consider coral reefs, which are dependent upon depth, if sea-level rises too quickly, the population of surviving corals may become too small to successfully colonize reefs in new areas. 

The answer to your question is complex. If you search the web for the term velocity of climate change you will find that your question is being actively researched by scientists.