You may try this (just a guide, but. that's more travel agent out there).
And from I know, Coach and Ferry (via Tg. Gemok), it took three and the half hour between Singapore and Tg. Gemok, while from Tg. Gemok to Tioman it took one and the half hour. Which means it took took 5hrs to reach Tioman.
But, if you took flight from Singapore (Seletar airport) to Tioman, it will took you only ~30mins.
Discovery Tours & Travel Pte Ltd
Working Hours
Address: 14 Scotts Road
#02-91 Far East Plaza
Singapore 228213
Tel: 6733 4333
Fax: 6733 4330
Email: sales@discoverytours.com.sg
Monday to Fridays: 0900 to 1800 hrs.
Saturdays: 0900 to 1300 hrs
Sundays and Public Holidays: Closed