Lots of boats offering boat tours. Yacht can also be chartered.
Dancing Fountains
A nice spectacle at night where fountains are operated to the sound of and music.
Georgia has a remarkable tradition of (royal) botanical gardens. It is a quiet spot, next to the Black Sea on a high cliff and it both green and cool. Plan on a visit here to take a half day to nearly a full day as it is very large. Expensive by Georgian standards but definitely worth seeing.
Statue of Medea and the Golden Fleece, near the Iranian/Azerbaijani joint consulate.
Kristos Amenaprkich
Built in 1885-87, this imposing church is fronted by a bell tower and was built diagonally to the street grid in the heart of old town Batumi.
Surprisingly good little museum with helpful and friendly staff. Georgian, Russian and English info and guides. Thorough background info, foreign coins, bronze vessels, glassware, ceramic, etc. Good collection of classical vases. Somewhat unpredictable opening hours.