Bosnia & Herzegovina is bordered by Croatia to the north, west and south, Serbia to the east, and also, Montenegro to the south.  Except for 26 kilometres of the Adriatic Sea coastline, the country is land locked.  Here's the map.

As Bosnia & Herzegovina only has a 26 kilometre coastline, the only location for diving is at the resort of Neum, which is on the Adriatic coast.  Unable to find anything of interest for the diving fraternity, except to say that if you do stay in Neum, the local hotels can arrange diving opportunities, but from what can be gathered, these expeditions would be in neighbouring Croatia.  There is also some diving that is done in lakes and ice diving during the winter.