My parents were divorced when I was 5. They had a strict schedule and stuck to it. (Monday/Tues. with mom and Wed/Thurse. with dad, alternating weekends). You should tell your x no more extra days and late drop offs. If they want to take her to the water, they can do it on their own day, and if they are "the adults" about it, they won't tell your daughter about the missed water park opportunity and she'll never know what she is missing.
Tell your husband that consistency, predictability, and routines are ESPECIALLY important for children of divorced parents. Your daughter needs to know that every Monday (or whatever day) she will be at dad's house and every Wednesday (or whatever) she will be at mom's house. No exceptioins. If my mom couldn't watch me on her day due to a business trip, she left me with my grandmother (not with my dad) and if my dad and step-mother had an anniversiary date, they hired a babysitter. This was not to be spiteful, but to stick to the routine for me.
If he doesn't believe it's important, tell him this...
Even though my parents DID keep the routine, I STILL have this dream to this day (and I'm 36) - I'm in high school and I have a basketball game, but I'm at my dad's house and my uniform is at my mom's house and I can't find it and my coach won't let me play without it and I can't figure out how to get to my mom's house to get it. I have variations of this dream (a project due at school, my pompoms for cheerleading, etc), but it always involves confusion due to my living at two houses.
STICK TO THE ROUTINE!! And if he doesn't abide, see the judge.
Remember, your daughter is most important in this case, not your ex-husband (or you).
So sorry he is doing to this to you. I hope he works with you.
Good luck,
A.