ripples are a very interesting case of study for game programming, AFAIK, GC takes care of all geometry on CPU, it send vertex data to GPU for render like OpenGL "immediate mode", the problem is that to make the ripples you have to modify the height of the vertex, is not a straight "take this data and render" you need to run a sine function on Y axis of each vertex with a variable that will change on your main loop each frame you can do that to a single water tile and just copy over and over to fill a lake or the sea that for the small waves and use a similar algorithm to modify the surface for the ripples on all water tiles depending where the character touch the surface on top of that , in modern OpenGL(and DX) you run this on a vertex shader program but on GC you run this on a CPU so it takes CPU time, while PS2 have the VU1 for that kind of work and Xbox have vertex pipes, back then( and for PS3) there was vertex pipes for vertex operations and pixel pipes of pixel/fragment operations now we use unified shaders like stream processors on PS4 and Xbox one that can run vertex or shader programs
there are many developers that expressed the GC lacking vertex processing power, this doesn't mean GC cant make the ripples, it means it can run into performance problems if you do too much vertex operations and other things require CPU time, again AFAIK I am not a GC developer, dreamcast(and n64, ps1 and saturn) also had this kind of problem, that and memory space problems forced devs to use basic shapes to build 3d models so they can use traslate operations instead of modifying vertex for animation or saving vertex positions
its weird to look a for the time high poly count model using this technique
this is for dreamcast, , a 4k+ triangles model is still a very respectable size in many games specially indies it has a lot of detail and normal maps techniques improve it a lot, the problem is that this technique ruins lot of detail, on PS1 games like crash bandicoot were very notable for using other techniques for their models instead but games that used other techniques or vertex modification was uncommon
for comparison this is for N64, we can see the huge improvement in polycounts