I had a holiday in south Goa last year before I went I looked on the web and found a guy called Tony Estrocio. I arranged two 4 hour boat sessions with him where I took my fly rod. On the first we went to a small reef. I persisted with the fly rod and lost jacks and snappers because I didn't have a wire trace on. Many fish slashed at my popper but did not get hold - exciting stuff.
The second trip we went up the main river system nearby and lost two Barramundi (trolling) they jumped in the air and went nuts. Then we caught several Mangrove Jacks. I tried my fly rod with some small Pacific Tarpon but to no avail.
The heat becomes overpowering by 11.00am - we started the fishing session at 7.00am but I'm really glad I did it, though it's not that cheap (there was only me in the boat). Sadly like so many places now Goa is seriously over-fished. If you were fishing from the shore try to get near a river estuary where there might be threadfin salmon.
Not sure how far Tony will be from you but I'll try to find the link.
Mick
Found that link:
http://goa-fishing.com/aboutus.html
Also hiring a taxi for the day (to stay with you) is very cheap even if it means taking you on a good journey to where Tony is based. Good luck