Hong Kong - Guangdong- Hong Kong

No, this is not possible for two reasons:

- Only the entry by air into Guangdong province is eligible for 144 hour visa free transit
- Your itinerary is just a round trip and not a transit. To be eligible for 144 hour visa free transit, your immediate points before and after mainland Chinese destination, in your case, Guangdong province, have to be in two different countries or eligible territories (eligible territories: Hong Kong, Taiwan and Macau).

To conclude, you can create an eligible itinerary to look like this:

Hong Kong - (by air) - Guangzhou - (by catamaran) - Macau

Exits from Guangdong are allowed overland, by sea or by other means, but an advance ticket bought online for a ferry is compulsory.