Depending on what you need in particular for this project you may be able to find some here: https://universe.roboflow.com/search?q=Dolphin
Btw, if you’re doing this for humanitarian/non-profit purposes we’d be happy to consider sponsoring it!
This DARWIN project for tracking dolphins is old but could be worth taking a look at too.
Boats doing hydrographic sounding are required to stay distant from dolphins similar. Currently they need an actual person (persons) to monitor. It would be good to make it easier and less expensive.