Check this section for info on Desire Riviera Maya before you post general questions in the other forums. Someone may have already provided a great answer for you here.
The actual walking distance (via the beach) from the south end of the edge of the Desire RM property to the Pearl dock(at the north end of the Pearl property) to is 3.1 miles (16574 ft) or in metric 5.05km (5051m). About an hours walk for the average person.....YMMV
THIS IS SOME GREAT INFO...ALOT OF TALK ABOUT REAL AND DESIRE BUT NO ONE HAS SAID HOW FREAKING FAR THEY ARE APART....SO A CAB RIDE IS LIKE 5-7 MINUTES FROM DESIRE RM TO PEARL??? WHATS THE CAB RATE?? OR IS THERE A CHEAPER METHOD TO GET TO PEARL?
We tried the walk, but there is a long section that has a break-wall and the water was slamming up against it, so we didn't dare try it. Ended up taking a cab, and with the road conditions, it took just over 20 minutes each way. Looks like it is a walk for the daring, or when the tide is very low.
We did walk to and from RM and Pearl and it's a little tricky in that one area cubman00 talks about. The tide was up and you can't see where to step - it's all by 'feel'. I know that you can arrange with the aquatic staff at RM to take you to and from the two resorts via a water taxi for a fee. I don't think they do this on a regular basis but if they have the time, they will do it.