There are two answers to your question
Yes in hot weather they love a muddy wet wallow and they will tolerate a certain amount in a wet spring or autumn,
No if they are permanently axle deep, have to find their food in it, its cold and full of their poo and wee (believe me it happens I've seem it!
)
In muddy weather feed in trugs or washing up bowls or troughs, regularly clean their water, make straw lakes so they have a dry area to retreat to, make sure their beds regularly have wet straw removed and dry straw refreshed in its place. When its really middy we bring our pigs into our buildings yes even in summer last year whenit was excessively wet as we're on clay and well its awful.
Use your common sense..........would you like to have to wade thro it for your food or a drink every time, or go out for a wee in it? Theres your answer!
HTH
mandy