in the area with all the crabs go to the poll farthest the the way you got in. swim thew the hole there and you will find the ship wreck. look threw the hole on the far side, then go to Ty's view. look threw the hole and you will see the tunder egg.turn the view and you will see a swich throw the boomerang at the swich and a door will open on the othe side.go the the doorand the next thing you know you have the thunder egg!

there is a small hole on one side of the bout go really close to it look throe the hole with ur scope and hit the button on the inside a door on the other sode will open go in and get ur thunder egg