These are the published times of the Isla Mujeres car ferry at the time of posting.The sailing times are fairly reliable, what is not so reliable is how long before the ferry leaves you need to be there. On ocasiones you can get there an hour before and still find it full, or get there five minutes before and find there is plenty of room to spare. There is a new Ultramar ferry which will soon be in use, the current ferry is difficult to date but probably goes back to the 1960's. So as you can imagine it's a bit basic when it comes to comfort.
A small car up to 4 mts costs 292 pesos and a larger vehicle up 6 mts, is 511 Pesos one way. The rules are always changing at one time that included one passenger and you had to pay for the rest. Then for a while they were refusing to take more that one passenger, so the other passengers had to walk down to Ultramar and catch the normal passenger ferry, We have heard recently that rule has changed. In any event it's not the end of the world those in the car can pick the other passengers up on the way into Cancun.
The Company does have a habit of changing the sailing times but not updating the website, it's the Caribbean so this type of unannounced change to a schedule is not unusual. If you are on Isla it's easy to pop down to the ferry and check the times, if you are coming from Cancun it's not quite so easy.
Isla Mujeres to Punta Sam (Cancún)
06:00 am 08:00 am 10:00 am 12:00 pm 04:15 pm 07:15 pm
06:00 am 08:00 am 10:00 am 12:00 pm 14:00 pm 16:15 pm 19:15 pm
06:00 am 09:30 am 12:45 pm 16:15 pm 19:15 pm
10:00 am 14:00 pm 19:00 pm
Punta Sam (Cancún) to Isla Mujeres
07:15 am 09:00 am 11:00 am 01:00 pm 05:30 pm 08:15 pm
07:15 am 09:00 am 11:00 am 13:00 pm 15:00 pm 17:30 pm 20:15 pm
07:15 am 11:00 am 14:45 pm 17:30 pm 20:15 pm
11:00 am 15:00 pm 20:00 pm