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I. Temperature and visibility.

a) Cold Water: Temperature below 70°F/21°C.

b) Thermocline: Sudden change in temperature in which a colder layer of water sits below a warmer layer of water.

c) Differences between freshwater and saltwater.

In comparison, salt water is denser than freshwater, and therefore heavier. This difference is clear between a freshwater swimming pool and the ocean as, all other things being equal, snorkelers will need more weight in the ocean in order to sink.

d) Factors that Affect Visibility:

  • The sea life that inhabits the excursion site.
  • Water motion.
  • The season.
  • Weather conditions.

II. Waves and breakers.

a) Wind and sismic events cause waves:

  • Wave Movement.
  • Breakers.
  • Backwash/Undertow.

III. Tides and currents.

a) Tides:

  • Cause.
  • Influence on excursion conditions.

b) Currents:

  • Cause.
  • Influence on excursion conditions.

IV. Underwater life.

Distribution of marine life is determined by:

a) Light:

  • Organisms that prefer light.
  • Organisms that prefer dark.

b) Seafloor Composition:

  • Organisms that live on hard substrates.
  • Organisms that live on soft substrates (e.g. sand).

c) Hydrodynamics (waves and currents):

  • All organisms that feed by way of filtering move and orient themselves with the currents.

V. Scientific classification: Taxonomy.

a) Family: Used to group similar genus.

b) Genus: The common scientific name given to different species belonging to the same genus.

c) Species: The specific scientific name given to individual species.

VI. Marine organism.

a) Vegetable:

  • Algae.
  • Marine plants.

b) Animal:

  • Sponges.
  • Cnidarian or Coelenterates.
  • Mollusks.
  • Crustaceans.
  • Echinoderms.
  • Fish.
  • Reptiles.
  • Mammals.

This academic session should provide suggestions on how identify the organisms they could encounter during a typical snorkeling excursion rather than focusing on proper scientific taxonomy and naming. This allows them to show many marine inhabitants to their customers. If candidate can show the marine organisms to their customers, other than make the excursion more interesting and enjoyable, they will have a great tool to   educating snorkelers to respect and conserve the environment.

VII. Marine environments.

a) Seagrass:

  • Poseidonia is a plant with roots, trunks and leaves.
  • They build an intricate habitat which is fundamental for the Mediterranean Sea.
  • Provide several environmental services:
    • Shelter for juvenile and reproduction.
    • Oxygen production.
    • Stability of the coastal seabed.
    • Protection the coast from erosion.

b) Coral reef:

  • Geographic distribution affected by:
    • Temperature.
    • Light.
    • Salinity.
  • Provide a complex habitat which is the most biodiverse of the ocean.
  • Threat:
    • Bleaching.
    • Global warming and acidification.


I. Human impact.

Human activities can lead to severe damages to marine ecosystems:

a) Fishing:

  • Stock reduction.
  • By-catch.

b) Pollution:

  • Accidental.
  • Indirect.
  • Not instantly recognizable.

c) Eutrophication:

  • Algal bloom.
  • Produce hypoxia.

d) Invasive species:

  • Organisms coming from far regions which spread in a new habitat.
  • They do not have natural predators.

e) Ocean acidification:

  • Most of the carbon dioxide is absorbed by the sea.
  • It decrease the pH, threatening the calcifying organisms.

Explain your candidates that their behavior and their daily choices contribute to marine protection.

It is the SNSI Snorkeling Guide’s responsibility to promote any kinds of marine conservation actions.

Remind them that their passion and their professional career rely on the marine ecosystems.

II. Your customers’ experience.

a) Before the excursion:

  • Responsible Snorkeling Center, which takes care about marine preservation:
    • Anchoring methods.
    • Manage the boat pollution.
    • Promote the waste reduction and recycling.
  • Learn more about the local environment:
    • Aware snorkeler.

b) During the excursion:

  • Swimming style.
    • Avoid hitting their fins against the organisms.
    • Avoid agitating the sediment.
  • Respect all marine life.
    • Never touch marine organisms; this can dangerous to both the organisms and them.
  • Do not feed any fish.
    • This modifies their normal behavior and creates imbalances in the food chain.
  • Never remove organisms from their habitat.
    • Also dead organisms (or parts of them, e.g. shells) have a function in the ecosystem.

c) Always:

  • Don’t litter.


I. General advice.

a) Surface traffic.

  • Importance of surface floats.
  • Mark the snorkeling area whenever possible (boundary markers).

b) Water visibility.

  • Influences the enjoyment and success of the excursion.
  • Attention to customers who freedive.

II. Night excursion.

a) Parameters of the night excursion.

  • From sunset to dawn.
  • Choose a place where you have already visited during the day.

Explain your students that it is fundamental to do a night excursion in a site that they already visited during the day.

Other than reducing the stress, this also allows to see how different the same environment is at night.

b) Reasons for the night excursion.

  • Some fish, which sleep at night, are easily approachable.
  • Some fish come out of their lair the night to hunt.

c) The gear for the night excursion.

  • Excursion from the shore:
    • Surface light to signal the exit: two lights placed at different heights, one on top of the other.
  • Boat excursion:
    • The boat should have enough illumination for people to see properly while getting ready for the excursion.
    • Strobe lights on the main surface float.
  • Underwater lights:
    • Primary Light:
      • With rechargeable batteries.
      • With disposable batteries.
  • Secondary lights:

Explain your candidates they should have few spare lights, in case theirs or customer’s ones run out

d) Night orientation.

  • Choose a site where you have already visited during the day.
  • Dark adaptation: ability to see in low light conditions.
    • A sudden light strikes the people’s eyes:
      • Immediate loss of the adaptations to seeing in the dark.
      • You need 5 minutes to recover the ability to see in the dark by 50%.
      • You need 30-40 minutes for complete recovery.

e) Doing a night excursion.

  • Excursion planning:
    • Environmental conditions: during a night excursion, environmental conditions must be perfect otherwise the excursion must be cancelled.
    • Surface staff: it is important to have a qualified person on the surface that can provide assistance if necessary.
    • Procedure to follow if you miss the group.
  • Night communication:
    • Signals using the light.
      • OK.
      • Calling the attention.
      • Something is wrong.

Never point the torch straight at your buddy’s face.

  • Pre-excursion check:
  • Buddy check. It is essential to carefully check the gear specifically needed for the night excursion:
    • Make sure all the torches work properly.
  • Enter the water only when both buddies are ready.

Explain your candidate it is fundamental that before any night excursion they revise the communication signs and the safety procedures.


III. Drift excursion.

a) Tide.

  • Main cause: Sir Isaac Newton explained that ocean tides result from the gravitational attraction of the sun and moon on the oceans of the earth.
  • Tides:
    • Spring tide: maximum tidal width.
    • Neap tide: minimum tidal width.
  • Factors determining tidal range:
    • Morphological characteristics of the coast.
    • Water depths.
    • Location.
  • Tidal period.
  • Tide tables.
  • Tidal currents:
    • Flood Flow: the tidal current is in flood when it is coming from the sea to the shore (tide is coming in, or high tide is ensuing).
    • Ebb Flow: the tidal current is in ebb when it is coming from shore and returning to the sea (low tide ensuing).
    • Slack Water: the point between flood and ebb (or ebb and flood) currents when there is no horizontal movement.
  • Stand: the point where vertical changes stop as the tide reverses. This is not the same as slack water; this is a tidal (vertical) occurrence, not a tidal current (horizontal) occurrence.

b) Currents.

  • Causes of currents:
    • Tides.
    • Earth rotation.
    • Water tendency to re-establish the hydrostatic balance.
    • Difference in atmospheric density.
  • Costal currents.
  • Backwash currents.

d) Excursion with current from the shore.

  • Always start the excursion against the current.

e) Boat excursion.

  • Always follow the captain or boat leader’s instructions.
    • Inform your candidates that usually the captain represents “the law” on board.
    • On boat, the snorkeling guide can be the one in charge.
  • Detailed boat briefing.
  • Detailed pre-excursion briefing:
    • Entry method: it changes depending on the kind of boat and the environmental conditions.
    • Information about the excursion route and safety procedures.
    • Exit method: it changes depending on the type of boat and on the environmental conditions.

f) Take decision regarding boat excursion.

  • Anchored boat.
  • Drift excursion.
  • Factors affecting the choice:
    • currents strength.
    • distance to cover during the excursion.
  • Entry from an anchored boat, exit with a moving boat.
  • Entry and exit on a drift excursion.

IV. Wreck excursion.

a) Wreck.

  • Natural.
    • Historical interest, more fascinating but also more dangerous.
  • Scuttling.
    • Sink specifically to create a point of interest.

b) Wreck types.

  • Depths:
    • Emerging.
    • Underwater.

c) Safety procedure.

  • Metal sheet.
    • Possibility of injuries, particularly when emerging.
  • No direct access to the surface.
    • Avoid freedive in the wreck, in case of difficulty it is not possible to return directly to the surface.


At the end of this session students have learned:

  • Procedure to apply for environmental protection.
  • Safety procedures for different types of excursions.


  • Tell the candidates the time, date and location of the next academic session for the final exam.
  • Tell the candidates the time, date and location of the next water session.


  • Training Record: Both you and the students must initial and date in the appropriate space in the training record section for academic session 4.