You can go straight from the Cebu South Bus Terminal to Dumaguete on a Ceres Liner bus-and-ferry combo via Liloan-Santander...Google can be a wonderful tool

Direct fast ferry (OceanJet) Total travel time: about 4 hours to 4 hours 20 minutes This is the fastest direct public transport route from city center to city center. Departs: Pier 1, Cebu City Arrives: Port of Dumaguete Route: Direct ferry, with a short 20-minute stop at Tagbilaran, Bohol (passengers stay on board). Schedule: Leaves Cebu daily around 8:20 AM. or South bus or driving + short ferry crossing Total travel time: about 4.5 to 5 hours This route gives you the most flexibility on timing during the day. Step 1 (land): Drive or take a Ceres bus from the Cebu South Bus Terminal south to Liloan Santander Port (about 3.5 to 4 hours). Step 2 (ferry): Take a fast craft or pump boat across the Tañon Strait from Liloan to Sibulan Port (about 20 to 30 minutes). Step 3 (short land ride): A quick 15-minute tricycle or jeepney ride from Sibulan Port takes you straight into downtown Dumaguete.

Tie some sea turtles together and just steer them the right way 🤣

25 minutes by air on Cebu Pacific.

Google Cebu City to Dumaguete and look up Rom2Rio, and you'll get 5 options. You decide what's "best" for you.