As well as the Star Ferries that just take you from one side to the other (best 20p you'll ever spend!), there's also a circular harbour tour route. It runs every hour and for most of the day costs HKD 40 (a little under GBP 3 at the moment).
At 7pm it jumps to HKD 80, then at 8pm to HKD 120.

My tip would be to get the 6:05pm one - the last HKD 40 tour. We went at the very end of August and it was just getting dark while we were on the boat. Getting to see all the skyscrapers of Hong Kong light up a bit at a time is pretty magical.

The best way to travel from Hong Kong to Kowloon, with great views of both from the water. A good chance to get some snaps of the skyline too.

We took the Star Ferry across from HK Island to Kowloon on 1st Nov. It cost us each only HKD$2.20. The ferries come every 10 mins so there was minimal waiting time. It was clean and comfortable and the ride gave us a fabulous view of the skyline. It's very convenient to reach Nathan Rd from the ferry terminus. We went into Sogo and took the escalators down to the underground crossing which was nicely airconditioned and with shops along the way. We got out from the Sheraton shopping arcade onto the main street of Nathan Rd. The ferry is an easier and faster way to get to Kowloon than it is by cab. We took a cab back to HK Island's Central from Kowloon and there was a slight traffic hold-up at the tunnel entrance. There seems to be perpetual traffic congestion when heading to Kowloon from HK Island via the tunnel link.

This is the one of the most romantic journeys you can make. Travelling from Kowloon to Hong Kong Island with the mass of neon lights in the background is the perfect place to propose.

Neil from Cheltenham