That looks like a fun project! If possible, stay away from painting the pool.
The pipe going to near the bottom in the deep end is most probably a suction line. And it will create an entrapment hazard. Any open suction pipe in the water without an approved VGB compliant cover is dangerous.
Yeah I'm pretty positive it is suction. I'll look into the cover to put on it if we don't get the pipes fixed before people start using the pool. Those pipes were a temporary fix when they thought the others were leaking. I'm hoping maybe it was just clogged and not broken.