I will repeat some of LadyLinda's questions earlier in this post:
On the path to the 2nd medallion, did something happen that you had to avoid?
For the tiki race, did you read the board in the observatory?
You can submerge down in the water, yes?
You have to follow the fish to find where the tikis are.
Also, if you are playing in Amateur mode, what things need to be completed on your tasklist?