Cozumel

🇲🇽 Cozumel is an island in Caribbean Sea off the eastern coast of Yucatan Peninsula in Mexico, opposite to Playa del Carmen. Cozumel reef is part of Mesoamerican Reef, the second largest barrier reef system in the world.
The Cozumel reef itself is classified as plateau reef because of its landscape. The reef stretches parallel along the coastline of the island. 

Cozumel is considered one of the best diving destinations in the Caribbean with it's crystal clear water, wide diversity of dive sites and it's accessibility. It is also famous for its strong current and drift diving. There is constant current going from the south to north which bring the nutrients to the reef. Most of the dives here would be drift dives.

How To Get There?
Some places have direct flights to Cozumel, such as Houston, Miami, Dallas in the United States and Toronto & Montreal in Canada. (these may have changed since)

If your location does not have direct flight to Cozumel, you can choose flying to Cancun Airport (CAN) or Mexico City Airport (MEX) for transferring to Cozumel (CZM). Maya Air has a direct flight from Cancun Airport and Volaris has a direct flight from Mexico City.

If you do not mind taking the land route, Cancun Airport is the closest airport to Cozumel. After arriving in Cancun Airport, you would need to transit to Playa del Carmen by car or by bus, from there you could take the ferry to Cozumel. 
   ✈️From Cancun airport to Playa del Carmen 
        By Car - around 45 minutes
        By ADO bus - around 1 hours 
   ➕ ⛴ Ferry ride around 45 minutes

There are two companies that operate ferries to Cozumel, Ultramar and Winjet. They run different time schedules on even and odd days. I highly recommend you to check their Facebook page for an updated schedule.
If you want to avoid the long queue (sometime the queue can be long for the morning and evening ferries) you can purchase the ferry ticket in advance through their respective websites. Get there early to make sure you have the spot. 

How To Dive There?
Boat Diving
Since the reef stretches parallel to the island, you can reach to most of the dive sites within 30 minutes by fast boat with double engine though not every dive shop has fast boat.

You will find many options of dive shops in Cozumel. Most of the dive shops typically run dive trips on the main reef (inner side of the island) from the dive site Maracaibo at the south to dive to Barracuda in the north.
Some dive shops charge extra for some dives sites where it is far south or far north, such as Devil’s throat and Maracaibo at the south and San Juan & Barracuda at the north and you might need to arrange it in advance.
Some dive shop do not charge extra, just treat every dive site as their normal daily dive site choices. You may need to take this into consideration when picking a dive shop.

Apart from diving at the main reef, based on what I know, only Aldora Divers and Salty Endeavors run dive trips to Eastern reefs of the island and only Aldora Divers run trips to Northern reefs (dive sites like Northern Wall, Tiburico etc). The eastern reef trip does not run often. 

Another thing to be aware of is that Cozumel Marine Park has a rotation of reef closures for different dive sites around the year to allow the reef rest from divers and boat traffic. You may want to keep an eye on it in your dive trip plan. 

This is the closure schedule for 2022 (the schedule could be changed, it could be found in their Facebook - Parque Nacional Arrecifes de Cozumel y APFF Isla Cozumel):

Shore Diving
Apart from diving on the main reef, there are some very accessible shore dives right outside Tikila Bar and Sunset Bar. They are close to shore, so it is more protected, the current generally is more gentle and mellow compared to the main reef.
Because of that, a lot of dive shops take students here to conduct diving courses.

The reef has slight slope down to a flat platform, most of the parts are within 10 meters  (33 feet) deep. The coral formations are not as many or as big as the main reef, but the marine life is pretty awesome. If you like macro diving, this might be a place for you. 

Shore diving is a great option for its good price, you could rent a tank with weight for USD10 or less. You can also hire equipment there as well. It is a great option if you want to dive by yourself and your buddy and take your time to hunt for small critters. It is also a great place for night dive due to its mellow current and you could see different sea creatures at night. 

Please make sure you can manage yourself to dive without a dive guide and you are knowledgeable to know what to do with different scenario, remember you are always responsible for your own safety.

Here is some useful information and my shore dive experience in Cozumel.

When To Dive?
You can dive in Cozumel all year around. Water temperature is between 25-28°C (78-82°F), slightly cooler in winter months. Some people prefer to avoid hurricane season from June to October as hurricane could hit Cozumel. 
Eagle ray season is from December to February. 

My Diving Experience & Highlight

Amazing underwater cave and pinnacle formation
Cozumel has amazing underwater caves and rock formations. Beyond the dive site of  Palancar towards the southern point (including Palancar, Columbia and Purta Sur), there are a lot of giant rock formations & pinnacle formations above the drop off.
The dive sites are full of cave, cavern spaces and tunnels. Some are open and wide and some could be very narrow.

The cavern system in some dive sites is massive, like a maze. All the rock formations are very amazing. You would expect a lot of swim through on these dive sites. Sometimes you may even exit at the drop off which is really amazing. It is very fun and challenging.

One of the well-known dive site, called Devil's Throat, is a huge underwater cave formation, considered one of the "must dive" dive site in Cozumel.
It is full of passages and spectacular chambers. You can explore the dive site in so many ways and go through different passages and exit at different spots. It was a fantastic experience for me. The formation is just spectacular!

These dive sites also have awesome coral formations, full of rope sponge, giant barrel sponge, tube sponge, sea fan, brain coral etc.
The marine life is not as concentrated as other dive sites in Cozumel, you could occasionally encounter turtles and sharks, and have higher chance to see pelagic marine life (eg. spotted eagle rays) in these area.
Some dive sites (like Palancar Garden) has a platform formed above the rock formation at the shallow area, you would expect to see more marine life on the platform.
Even with relatively less marine life, this part of the reef is really worth to dive. 

Just be aware that current sometimes can be strong in those dive sites. Also, you sort of need certain level of buoyancy control for all the swim throughs.

Sight of spotted eagle rays
Cozumel is a great place to see spotted eagle rays with a very high probability.

Spotted eagle rays is one of the biggest eagle rays, their body is in deep blue or black colour with white spots on top and really long tails. Their size can be up to 5 meters (16 feet) in length with a wingspan of up to 3 meters (10 feet). It is such an elegant and beautiful sea animal. 

From December to February ("the season"), spotted eagle rays appear in the reef in Cozumel, we still not fully understand the reason, it is believed that Cozumel is one of their migration point. They come when the water temperature is colder during those months.

During the season, you have very high chance to see them, particularly at southern dive sites beyond Palancar or northern dive sites beyond San Juan. If you are lucky, sometime you can see a big group of them more than 10. Some dive guides who work in Cozumel said you could see them almost everyday during the season, of course there is no guarantee for it. Sometimes they just pass through the reef and sometime they feed on the sandy bottom which you have a chance to get closer to look at them. 

I was in Cozumel during the off-season months between June and October and I still encountered them on and off sometimes. For my personal experience, the time when I was diving almost everyday for a month, I saw them once a week or 10 days and normally it was solitary. So there is still chance to see them even in the non-season months, but the chance is definitely lower.

Plan you trip in the spotted eagle ray season, it is an amazing experience to see them. They are definitely a reason for me to go back to Cozumel. 

A very special creature - splendid toadfish - they look splendid!
If you did not have chance to see the spotted eagle ray, no worry, there is other special creature that you can see in Cozumel which you would not see in other places. It is  splendid toadfishes! It is a must see when you are in Cozumel.

This species only live along the eastern coastline of Caribbean Sea from Mexico to Belize, even along the coastline, you do not see them often, but they are commonly found in Cozumel. Since toadfish do not swim great distances, their populations become isolated by geography and concentrate at some spots and Cozumel is that spot! 

Splendid toadfishes are a very colourful fish which have quite a special funky look. Personally I think they look quite cute. Their head are in sky blue and black colours in zebra like pattern with many branched barells particularly at the lower jaw. Their body are in dark grey, have faint chain-link pattern, look very different than the head.
They live under small edges in the reef or in small rock crevices or crevasses, they are quite hidden most of the time, so typically you can only see their head poking out from the rock crevices.

In Cozumel, you can easily see them in some dive sites eg. Paso del Cedral, Yucab, Punta Dalila or Villa Blanca. Ask you dive guide, they know where to find them. Do not miss them if you are in Cozumel. They look splendid!  

Is it worth to go?
It depends. Cozumel has its charm. I personally think Cozumel is one of the best dive destinations in Central America or in Caribbean Sea. If you are from this side of the world, it is a great dive destination for its convenience and a great choice in Central America. If you need to travel far to get there, there are a lot of dive destinations which is more awesome than Cozumel considering the biodiversity aspect. 
Nevertheless, it is definitely worth to visit the spotted eagle rays there. 

Other Useful Information

Above information based on dive trip from June to October 2021.