There are options to go to Barisal by water or by road, but going to Barisal by water is the most convenient way.
If you want to go to the launch : From the Sadarghat launch terminal in Dhaka, several launches travel to Barisal every day and arrive between 4 and 5 in the morning. Deck fare per person to Barisal is Tk 200, single cabin fare is Tk 900 (non AC) and double cabin fare is Tk 1700 (non AC). From Barisal launch ghat by auto or rickshaw to Chaurasta and by bus to Swarupkathi launch ghat will cost Tk 50 fare.
You can rent a trawler from Swarupkathi launch ghat and enter through Sandhya river and visit Atghar, Kuriana, Bhimruli market. If you bargain, it will cost 1000 to 1500 rupees depending on the trawler. Or you can come to Kuriana Bazar by renting an auto from Swarupkathi Launch Ghat for Tk 20 to Tk 300 and rent a boat or trawler for Tk 200 to Tk 300. But if you go to Bhimruli, the fare will be more.
Besides, if the road is good, you can visit Atghar, Kuriana and Bhimruli market by auto. In this case, do some research or because some bridges are broken, you have to come to each bridge by auto, cross the bridge on foot and take the auto again.
If you want to go by bus : Several buses depart from Sadarghat and Gabtali bus terminals in Dhaka via Padma Bridge for Barisal. Sakura Paribahan bus ticket price to Barisal is 535 to 1250 taka per person. There are direct buses from Gabtali to Swarupkathi launch ghat. Sonar Tari, Hanif and Sakura transport buses cost Tk 500 per person. You can visit Barisal or Swarupkathi by bus and visit the floating guava market in the above mentioned way.