Hi batakbule...

I  think there is a public boat services from haranggaol to Simanindo, its probably once in the week?every wednesday, when there is a market in Haranggaol. Then from  Simanindo you can get a public transport just until the junction of tuk tuk ( where you can have lots choice of accomodation/hotel ), then you pay like Rp.7000, but it is best to ask the driver to drop you off in Tuk Tuk, then pay extra cost, depend on how good you are bargain.

Other wise, there are some hotel in Tuk Tuk like Samosircottages (see their site www.samosircottages.com )that you can call, so they can pick you up to Simanindo.

An other option is that you take a bus from Haranggaol to Parapat, and then take a boat to Tuk tuk, the boat run every hour and the ticket is Rp 7000. The boat will drop every passengger off in any spot arraound Tuk Tuk peninsulla.

Hope this info could help you