Semarnat Delegate in Quintana Roo diving with the Bull Sharks at Phantom Divers.

On March 4th 2017, we had the honor of diving with Renan Sánchez at Phantom Divers who is the Delegate of Semarnat in Quintana Roo. He accompanied us on our legendary Bull Shark diving, so he had the opportunity to live this amazing experience. We talked about the marine life importance in the ecosystem, including the Bull Sharks that visit Quintana Roo every winter. He knows about the big efforts of Saving Our Sharks for the protection and conservation of the Bull Sharks, and is really proud of all the work done. 

Underwater Comunication

UNDERWATER COMUNICATION

Diving allows an opportunity to be with our own thoughts and provides the peace necessary to stop and appreciate the natural beauty of the world around us.

Part of the underwater world’s charm is its relative silence, the opportunity that it gives us to escape from the incessant ringtones and alarms of life on land. That we can’t communicate as we usually do can also pose problems underwater. Your entry-level scuba course would have taught you basic hand signals to convey important messages underwater signals are the backbone of a recreational diver’s underwater communication, and the longer you dive, the more intricate and elaborate your repertoire will become.

This is a simply overview of some of the most commonly used underwater hand signs. 

The "Okay" Signal
The first hand signal that most scuba divers learn is the "Okay" hand signal. Is made by joining the thumb and index fingers to form a loop, and extending the third, fourth, and fifth fingers. This signal can be used as both a question and a response. The "Okay" signal is a "demand-response" signal, meaning that if one diver asks another diver if he is okay, he mustrespond with either an "Okay" signal or the communication that something is wrong. The "Okay" hand signal should not be confused with the "Thumbs-up" signal, which in scuba diving means "end the dive."

The "Not Okay" or "Problem" Signal
Scuba divers communicate a problem by extending a flattened hand and rotating it slowly side to side, similarly to how many people signal "so-so" in a normal conversation. A diver communicating a problem underwater should then point to the source of the problem using his index finger.

The most common use of the "Problem" hand signal is to communicate an ear equalization problem.

The "Up" or "End the Dive" Hand Signal
A "Thumbs-Up" sign in scuba diving communicates "Up" or "End the Dive". This should not be confused with the "Okay" signal. The "Up" signal is one of the most important signals in scuba diving. The Golden Rule of Scuba Diving states that any diver can end the dive at any point for any reason by using the "Up" signal. This important dive safety rule ensures that divers are not forced beyond their comfort level underwater.

The "Down" Hand Signal
The "Thumbs-Down" hand signal communicates "go down" or "descend" underwater. This signal should not be confused with the "not-okay" hand signal used to indicate a problem. The "Down" signal is used in the first step of the Five Point Descent, in which divers agree that they are prepared to begin the descent.

The "Stop" Hand Signal
Divers typically communicate "Stop" in one of two ways. The first method of communicating "Stop" (common in Recreational Diving) is to hold up a flat hand, palm forward, as shown in the left. Technical Divers, however, favor the "Hold" sign, shown on the right, made by extending a fist with the palm-side of the fist facing outwards. The "Hold" sign is a demand response signal; a diver who signals "Hold" to his buddies should receive a "Hold" sign in return, indicating that his buddies have understood the signal and agree to stop and hold their position until otherwise indicated.

The "Level Off" Hand Signal
The "Level Off" hand signal for scuba diving is use to communicate "remain at this depth" or "maintain this depth." The "Level Off" signal is most commonly used to communicate that divers have reached the planned maximum depth for a dive, or to communicate that divers should hold previously designated depth for a safety or decompression stop. The "Level Off" hand signal is made by extending a flattened hand, palm down, and slowly moving it side-to-side horizontally.

The "Buddy Up" or "Stay Together" Hand Signal
A diver places two index fingers side-by-side to indicate "Buddy-Up" or "Stay Together". Scuba diving instructors use this hand signal to remind student divers to stay close to their buddies. Divers also occasionally use this signal to reassign buddy teams underwater. For example, when two divers in a group are low-on-air and ready to ascend, they may communicate "we'll stay together and ascend" using the "Buddy Up" hand signal.

The "Safety Stop" Hand Signal
The "Safety Stop" hand signal is made by holding the "Level Off" signal (a flat hand) over three raised fingers. A diver is indicating "Level Off" for three minutes (signified by the three fingers), which is the minimum recommend time for a safety stop. The safety stop signal should be used on every dive to communicate within the dive team that the divers have reached the pre-determined safety stop depth and agree to maintain that depth for a minimum of three minutes.

The "Low-On-Air" Hand Signal
The "Low-On-Air" hand signal for scuba diving is made by placing a closed fist against the chest. In general, this hand signal is not used to indicate an emergency, but to communicate that a diver has reached the pre-determine tank pressure reserve for his dive. Once a diver communicates that he is "Low-On-Air," he and his buddy should agree to make a slow and controlled ascent to the surface and end the dive by using the "Up" signal.

The "Out-Of-Air" Hand Signal
The "Out-Of-Air" signal is taught to all Open Water Course and Experience Course students so that they know how to react in the unlikely event of an out-of-air emergency. The chances of an out-of air emergency when scuba diving are extremely low when proper Pre-Dive Checks and diving procedures are observed.

Hand signals are generally international, but it’s always wise to make sure you, your buddy and the divemaster are on the same page. Understanding one another is imperative if a dive is to run smoothly, and can make all the difference in an emergency. 

Learn the signals used by local divemasters to describe local wildlife; often the more local animal signals are not universal and you could miss out on an exciting sighting if you don’t know what the divemaster is saying.

And remember to dive fun, dive safe and dive with Phantom Divers.

Cenotes

CENOTES

A cenote [seˈnote]; plural: cenotes; from Yucatec Maya dzonot or ts'onot, "well" is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater underneath. Especially associated with the Yucatán Peninsula of Mexico, cenotes were sometimes used by the ancient Maya for sacrificial offerings.

The term derives from a word used by the low-land Yucatec Maya — ts'onot — to refer to any location with accessible groundwater. Cenotes are common geological forms in low latitude regions, particularly on islands, coastlines, and platforms with young post-Paleozoic limestones that have little soil development.

Formation

Cenotes are formed by dissolution of rock and the resulting subsurface void, which may or may not be linked to an active cave system, and the subsequent structural collapse. Rock that falls into the water below is slowly removed by further dissolution, creating space for more collapse blocks. The rate of collapse increases during periods when the water table is below the ceiling of the void, since the rock ceiling is no longer buoyantly supported by the water in the void.

Cenotes may be fully collapsed creating an open water pool, or partially collapsed with some portion of a rock overhanging above the water. The stereotypical cenotes often resemble small circular ponds, measuring some tens of meters in diameter with sheer drops at the edges. Most cenotes, however, require some degree of stooping or crawling to access the water.

Penetration and extent

In the north and northwest of the Yucatán Peninsula, the cenotes generally overlie vertically extensive voids penetrating 50 to 100 m (160 to 330 ft) below the modern water table. However, very few of these cenotes appear to be connected with horizontally extensive underground river systems, with water flow through them being more likely dominated by aquifer matrix and fracture flows. In contrast, the cenotes along the Caribbean coast of the Yucatán Peninsula (within the state of Quintana Roo) often provide access to extensive underwater cave systems, such as Sistema Ox Bel Ha, Sistema Sac Actun/Sistema Nohoch Nah Chich and Sistema Dos Ojos.

Freshwater/seawater interface

The Yucatán Peninsula contains a vast coastal aquifer system, which is typically density-stratified.^[5] The infiltrating meteoric water (i.e., rainwater) floats on top of higher-density saline water intruding from the coastal margins. The whole aquifer is therefore an anchialine system (one that is land-locked but connected to an ocean). Where a cenote, or the flooded cave to which it is an opening, provides deep enough access into the aquifer, the interface between the fresh and saline water may be reached. The density interface between the fresh and saline waters is a halocline, which means a sharp change in salt concentration over a small change in depth. Mixing of the fresh and saline water results in a blurry swirling effect caused by refraction between the different densities of fresh and saline waters.

The depth of the halocline is a function of several factors: climate and specifically how much meteoric water recharges the aquifer, hydraulic conductivity of the host rock, distribution and connectivity of existing cave systems and how effective these are at draining water to the coast, and the distance from the coast. In general, the halocline is deeper further from the coast, and in the Yucatán Peninsula this depth is 10 to 20 m (33 to 66 ft) below the water table at the coast, and 50 to 100 m (160 to 330 ft) below the water table in the middle of the peninsula, with saline water underlying the whole of the peninsula.^[5]

Types

Radar topography reveals the 180 km (110 mi) ring of the crater; clustered around the crater's trough are numerous sinkholes, suggesting a prehistoric oceanic basin in the depression left by the impact (Image courtesy NASA/JPL-Caltech).

In 1936, a simple morphometry-based classification system for cenotes was presented.

• Cenotes-cántaro (Jug or pit cenotes) are those with a surface connection narrower than the diameter of the water body;
• Cenotes-cilíndricos (Cylinder cenotes) are those with strictly vertical walls;
• Cenotes-aguadas (Basin cenotes) are those with shallow water basins; and
• grutas (Cave cenotes) are those having a horizontal entrance with dry sections.

The classification scheme was based on morphometric observations above the water table, and therefore incompletely reflects the processes by which the cenotes formed and the inherent hydrogeochemical relationship with the underlying flooded cave networks, which were only discovered in the 1980s and onwards with the initiation of cave diving exploration.

Tarpon in Playa del Carmen, Mexico

In the last few days large schools of tarpon have been sighted in Sabalos Reef (Tarpon Reef) offering a great show.

Come to visit us and let us show you this spectacle as well as much more the Mexican Caribbean offers to divers.

Tarpon move in large schools 

This prehistoric fish which has a life span of 50 years is also called the "silver king" due to its majestic appearance of size and color

Tarpon (megalops atlanticus) can grow up to 8 feet and weight up to 280 pounds

The tarpon is the only fish able to absorb oxygen from the atmosphere due to their air bladder

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