No matter how you do it, a standard flamingo tour unfolds in four parts: a visit to the “petrified” forest (a stand of ghostly, leafless trees killed by saltwater intrusion), then to the flamingo feeding grounds, followed by a short ride through the mangroves, and then a stop at an ojo de agua (freshwater spring; literally, an “eye of water”) to go swimming. Because the sites are relatively far apart—the petrified forest is at the mouth of the ría while the flamingos congregate near its top, around 15 kilometers (9.3 miles) away—you spend a good amount of time motoring from one place to the next.
In a 2–2.5-hour trip, you’ll spend 20–30 minutes observing the flamingos (and somewhat less at the other spots). It doesn’t sound like much, but most people find it sufficient. If you want more time with the flamingos—especially if the flock is at its height—private guides are the most flexible. With either the state guide service or the fishermen’s cooperative, you’ll have to get everyone in the boat (and the guide) to agree to adjust the schedule.
The Parador Turístico Cultur is the rather inelegant name for the pier and visitor center where the state-sponsored guide service is based. It is two kilometers (1.25 miles) from Celestún , on the west side of the highway bridge spanning the ría. From there, you can book a complete tour (US$100, 2.5 hours) or a shortened tour that doesn’t include the petrified forest (US$60, 1.5 hours); in either case, there’s a US$2 per person park fee.
The people at the ticket counter won’t necessarily offer to put small groups together; the best way to join other travelers is to arrive around 10 a.m. (if you’re coming from Mérida  by bus, take the 8 a.m. departure) and ask around. Guide service is available in Spanish, English, and Italian.
The fishermen’s cooperative has a stand on the beach, at the end of Calle 11. Trips from here are basically the same, though you have to motor along the coast first to the entrance of the estuary, and the tour starts with the petrified forest. It cannot be shortened, as tours from the bridge can.
Tours cost US$85 for a private group (2.5 hours, up to seven people) or US$14 per person on a shared trip. If you end up waiting for more than an hour for a group to develop, captains often will take groups of 2–4 people for somewhat less.