Originally Posted by JohnSIN

If you go from Singapore CBD, say Bugis where the buses to cross the causeway start from, to Larkin, it will take you between 1 to 1h30 minutes, except for peak period.
From there, you are 1 hour drive to Desaru.

When going to Desaru, I prefer to take the ferry from Changi Ferry Terminal to Tanjung Belungkor and have a taxi waiting for me.
Beware that Tanjung Belungkor is in the middle of plantations and there would be no taxi waiting unless you have made prior arrangements.
I had on one occasion arranged for a car that didn't turn up. As it is 30 mins away from Desaru and where the hotels are, it took us an hour to get a replacement.

So in my book, it is Ferry + car. Get the hotel to arrange a car and reconfirm with them prior to your arrival.
The westin website doesn't suggest they offer hotel car and transfer but they would be working with local Taxi driver.