Caboose is definitely going to be a big boy when he grows up! He's absolutely gorgeous.
As for webbed feet, they are generally the characteristic of water dogs, eg. Spaniels, Setters and Labs and generally go with bigger feet in proportion to body size. However, any breed can have webbed feet in individuals, even if it's not a general breed characteristic. As with humans, all it takes is for 2 recessive genes to combine.
If you're green, you're growing...if you're ripe, you're rotting!
I try to greet the world like my pets do...boundless enthusiasm, intense curiosity and no concept of yesterday and tomorrow.