Ecco The Dolphin Wiki
   Locate the Recluse Dolphin, Distract the Giant Eel with a Giant Manta Ray
The large Crystal columns that are found in the tunnels will replenish your
air as long as they have a dancing light inside them.  Any Oysters that you
find in the level will replenish your health.  To release these goodies, simply
sonar the item in question.  The crystals will release the light and it
will travel over Ecco to restore his air, and the Oysters will open up to reveal
a Pearl.  Collect the pearl and Ecco's health will be restored.***

This level takes time & patience.  Try to rush it and you will most likely end
up in a wrong tunnel with no idea where to go.  From your start position,
travel into the central chamber and collect the Air Star Glyph.  This will give
you the ability to use the Air Glyphs which will extend you air supply,
and for this level you need as much air as you can get.  After collecting the
Air Star Glyph, turn so that you are facing a purple Guardian Glyph and swim
towards and past it until you see the cavern wall.  Along that section of wall
will be a tunnel with a small Eel hiding in the top of the tunnel entrance.

tunnel facing you, turn 90 degrees to your right and carry on swimming along
that sidewall (keep an eye on that air meter) until you see a section of the
wall turn light brown and looks like it is made of old brickwork.  It is high up
on the wall, much higher then the first tunnel, and has Sea Anemones in the
entrance.  You can stun these into retracting by sonaring them.  A small way
down this tunnel is an Air Glyph (YAY!), which will refill your air supply and
double its length from a full position as well.  After collecting the Glyph
continue into the tunnel until you reach a Purple Crystal Column.  From here
you can go left, right or ahead.

In the right hand tunnel is a Power Sonar Glyph, which you will need on your
return (Oh yes, you will come back here later in the game).  The left hand
tunnel contains the Recluse Dolphin.  If you travel all the way to the end of
the tunnel, ignoring the left hand turn about half way down the tunnel you will
enter an area with the Recluse Dolphin who will teach you The Ray Song if you go
back to the main area of the level and bring him the LARGE Blue & Yellow Fish.
The forward tunnel is just a dead end, but it has an air current to restore your
air if you are running low and have already used the Crystal restore.  Once you
have the Ray Song, exit this section of tunnels as quickly as possible and go
back into the central chamber.

Head towards the tunnel where you started and when you are looking towards your
start point, turn left 90 degrees and follow this wall until you find a very low
tunnel entrance.  This is called the 'Red Tunnel', as it has a Red Crystal
Column in it (remember the purple one?).  Once you reach the Red Crystal Column
you can go ahead or left.  The left tunnel serves no purpose except to waste
your time and air, both of which are precious in this level.  If you go straight
on down the forward tunnel you will come to a pool with sharks in it and a LARGE
MANTA RAY (you need him in a minute).  Kill the sharks.  Replace any energy you
may have lost in the fighting and collect the Air Glyph (helpful Guardian
again!) that is in the pool.

Make sure that you are facing the tunnel and the Manta Ray is between you and
the tunnel.  If you sonar the Manta Ray he will swim towards the tunnel, and
start swimming down the tunnel.  Stay behind him and keep sonaring him until you
exit the tunnel.  Once you exit you need to aim the Ray about 45 degrees to the
right of the tunnel you just came out of, as this puts him swimming towards the
Giant Eel in the roof that would usually eat Ecco and end this fun rather early.
If you're still not quite sure where to aim him, just look for a floor-to-
ceiling column of rock.  The Giant Eel is hiding behind this.  Make the Ray swim
towards this area and as soon as you see the Eel dive out of the roof, CHARGE
like mad past him and into the tunnel beyond.

Think that's it?  OH BOY, ARE YOU WRONG.  We can't let all these fun and games
end quite so quickly, can we!  Head down the tunnel (beware, its LONG) until you
get to a 'collar' of rock similar to the one that the Air Glyph was in.  Beyond
this is a small air column that you can refresh your air with.  Just beyond this
you will see another tunnel, but it will have a strong current, which will stop
you progressing.  OH NO, no Vigour Glyph, what do we do!  Never fear, here is
the answer.  The rocks above this tunnel are loose, and if you nudge one it will
fall down the tunnel and block the current BUT you have to follow the rock down,
as it will not block the current permanently.  Once you are past this the tunnel
will split into two.

The right hand tunnel has the fish that cure jellyfish stings, so if you do get
stung here, go right and heal yourself.  The left tunnel will lead to a four-way
junction with a VERY BIG Blue Crystal Column in the middle of it.  The ONLY
tunnel of importance here is the right hand one.  If you travel down this tunnel
a short way it will split into two.  The right hand side has an Oyster if you
need to replace Ecco's energy.  If you don't need to head to the right then take
the left hand fork and swim like hell as from this point on it is a straight
race between you and Ecco's lung capacity.  Keep travelling down the tunnel,
ignoring any other turns, as they are of no importance to you whatsoever.
Eventually, after what seem like miles of tunnels, you will see another rock
collar (remember them?), which signifies the end of the level.  Travel through
it and keep swimming until a cut-scene takes over and shows Ecco swimming
upwards and
 back to Perils Of The Coral Reef (Nope, I'm not kidding).