Assuming you lower the pH first before shocking to the high FC level, then the active chlorine level will be roughly equivalent to a pool with 1.4 ppm FC with no CYA. This is roughly the level found in indoor commercial/public swimming pools. The chlorine (and chloramines) in such pools is usually noticeable and continued swimming in such pools usually results in swimsuits degrading, flakier skin and frizzier hair. Chlorine reacts with everything faster at this level so would produce disinfection by-products more quickly so you'd likely smell it on your skin more.
If someone did get into a pool at such high FC levels, then when they get out they should rinse off right away. This is because the high FC level will continue to react with your skin when you leave the pool and that will last much longer than a lower FC level and if you let that water evaporate, then that chlorine becomes more concentrated.
We don't recommend getting into a pool higher than normal shock level, but that's mostly to be conservative and not having enough experience with anyone using a pool at higher levels.
Swimming with algae is not unhealthy, but if the pool is cloudy so that you cannot see the bottom very well, then that is dangerous since you wouldn't be able to see someone who is drowning. Algae can also be slippery so that would be another hazard.