Desmond's boat

• probably located somewhere near the crater (see crater)


• maybe not seen by the Losties because there is a cliff around the bay (see screenshot)

Crater

• The location of the crater can be seen on Rousseau's map (e.g. here)
• Area passed by Rousseau, Kate, Locke, Jack, Hurley and Arzt in S01E23 on their way to the Black Rock (see screenshots)
• Area passed by Charlie and Sayid in S01E24 on their way to get back Aaron
• Probably the same location as the "unpassable area" (see Unpassable coast area)
• Probably the position of Desmond's boat
• Edit (04/15/07): The place seen in S03E16 where Juliet talks to Ben about her sister seems to be in a similar terrain (see 4th screenshot). Thanks to Kimeee for alerting me to this

Unpassable coast area

• Taillies could not pass this area in S02E06
  
• Probably the position of Desmond's boat (see screenshot)
• The brown rock surface might indicate that it's close to the crater
• Similar area passed by Rousseau, Kate, Locke, Jack, Hurley and Arzt in S01E23 on their way to the Black Rock (see Crater)
• Similar area passed by Charlie and Sayid in S01E24 on their way to get back Aaron (see Crater)