According to Pennsylvania State Professor A. J. Turgeon, writing in his excellent textbook called Turfgrass Management, 9th Edition, tall fescue has a high submersion tolerance, second only to creeping bentgrass, while fine fescue has the lowest submersion tolerance among the cool season grasses. Kentucky bluegrass and perennial ryegrass are near the bottom too, just above fine fescue.
For the warm season grasses, seashore paspalum ranks the best for submersion tolerance, followed by bermuda. Zoysia and centipede rank near the bottom. St. Augustine in the middle.
Bermuda wouldn't work as a solution for my neighbor because his side yard gets a fair amount of shade. That leaves tall fescue as his best choice for grass there because creeping bentgrass ranks in the bottom half of popular turfgrasses when it comes to tree shade tolerance.
Fine fescue, of course, is an excellent shade grass, but again, it doesn't do well in submerged conditions. So tall fescue would be a good choice for him there.