I think there are several new traits that should be added:

"Hates shampoo" (after his daddy drowned in the bathtub and he witnessed the horror, this man dreads water more than anything; +4 squalor, +25% cost when building sanitary improvements)

"Inefficient swimmer" (this man's family has a history of deaths in water; -2 command in bridge battles, +3 extraweight when charging)

"New retinue: lifeguard" (some have a talent to be at the right spot at the right moment; +2 drowning points - the number of underwater crossings in a bridge battle that your general can withstand - and extra lifebuoy for each upgrade of sanitary facilities)