I guess an argument could be made that since it says your maximum movement for the round, not a round, it already uses whatever movement speed applies during that particular round. What I find to be far more interesting is the problem with trying to use multiple movement types as part of the same move action. I mean, if I jump into the water when I've still got plenty of movement left in the round according to my land speed, but I have a much lower swim speed, what happens? I'm pretty sure the rules just don't say anything about it, and this isn't a gap easily filled by common sense.