Scuba Diving

More then two thirds of our planet's surface is covered with oceans, lakes and rivers, while waterfilled caves and passages are hidden beneath much of the dry land. These submerged realms are strange and full of wonders. To many of those who visit and study it, the underwater world seems like a different planet; and even after centuries of exploration and scientific research, it continues to hold many mysteries and surprises.

Through scuba diving, we can visit and explore the underwater world. Scuba equipment enables us to breathe, swim and see underwater; it includes:

a tank (filled with compressed air)
a scuba regulator (which delivers the air to the diver), consisting of
- a first stage
- a pressure gauge
- a primary second stage with mouth piece
- a backup second stage with mouth piece (for emergencies)
- hoses (to connect it all)
a buoyancy compensator (which helps to hover effortlessly midwater)
diving fins (for more effective swimming)
a diving mask (enables good underwater vision and protects the eyes)

Scuba diving requires some instruction, but it is not hard to learn; courses are offered, for example, by the UBC Aqua Society.

Many sea mammals are much better divers than humans are. For example, they easily outswim even scuba divers using the most advanced fins, as can be seen from this table, showing maximum sustained underwater swimming speeds (source: http://www.elasmo-research.org/education/topics/r_haulin'_bass.htm):

creature	speed
Pacific Whitesided Dolphin	27 km/h
California Sea Lion	40 km/h
Killer Whale	56 km/h
scuba diver (with fins)	5 km/h
scuba diver (without fins)	< 3 km/h

However, with brute force, humans can beat the fastest swimmer in the ocean: The fastest nuclear submarines (Russian alpha class) reach a speed of 74 km/h (source: Guinness Book of World Records).

But swimming fast is not what diving is all about - quite on the contrary, it is a rather relaxing, sometimes meditative experience.