Zhongshan port goes to Hongkong by boat, a one-day tour guide.

If you just want to see the scenery and take a one-day tour (assuming you arrive in Hong Kong in the morning), I suggest you take this road:

To the seaside of Stanley: Take bus No.6 and No.6x at the Central Bus Terminal and get off at Stanley Terminal (it is close to the sea along the way and has excellent scenery).

To the Peak of Taiping Mountain: Come back from Stanley or take bus No.6 or 6x to get off at Central Bus Terminal, and then take bus 15 to the Peak of Central Bus Terminal.

Go to the Avenue of Stars: After sightseeing, it's probably almost evening. Go back to Central Bus Terminal, walk about 10 minutes to central ferry piers, cross the sea by Star Ferry, and expect to arrive at Tsim Sha Tsui Pier in 15 minutes, with the shopping mall (Harbour City) on the left and the Avenue of Stars on the right. Enjoy the night view!

I hope I can help you. Have a nice trip!