Is there any high speed train from Shantao to Xiamen and Vice versa? How long is the journey?

You must refer to Shantou, right? Well, no ferry is available for this route and train shall be the best way to go.

From Shantou Central Bus Station, General Bus Station or China Travel Bus Station, you can take a direct shuttle bus to Chaoshan Highs-speed Train Station (or take bus no. 181 from Shantou Yidu Theatre to reach). There you can easily catch a fast train to XM and it takes around 1.5h to arrive. It costs CNY73.5 for a first class seat and CNY61.5 for a second class seat. For the back trip, you can use the same way.

Except purchasing ticket on the spot, you can also book the ticket. Then you are suggested to turn to Travel China Guide. They have great service and charges just a little service fee. If needed, here is their contact for your reference:
bookingtravelchinaguide.com