Since Cozumel has a tropical savanna climate, you will notice that the temperatures are fairly high most of the year. As a result, you can take the ferry Cozumel at any given time. You can check out the Playa del Carmen, embark in a Cozumel day trip or take the Cozumel boat to explore the region.
You can take the Cancun ferry or the Tulum ferry that bring you to Cozumel. These Cozumel ferry options tend to depart at least a few times per day, if the weather is good, they might even go hourly. You will find the exact schedules for that day when you arrive. It also depends on where you are departing from, as the Tulum ferry can have a different schedule when compared to the Cancun one for example.
As we mentioned earlier, the Cozumel ferry schedule is hourly, unless stated otherwise. If you go to Cozumel, the schedule is hourly from 7 AM to 11 PM, if you go to Playa del Carmen it will be from 5.45 AM to 11 PM, with hourly rides from 7 AM.