1. To keep the Dolphins from going deeper and to also know were they are the first dolphine you catch put him on a balloon or float with a 10' 30# leader and put a hook in it's mouth. Mouth only, so the dolphine can swim correctly. Do this to two or three dolphine. The school will not dive deeper. Plus you will know were the school is at.
2. Dolphine bombs. Take any bait you prefer to use, I use scallop guts. Go to the beach and get some sand. Take the bait and the sand and mix then together. Now make balls with the mix and chill in cooler. Next time the dolphines are deep and you want to get there attention. Drop a couple of bombs on them. As the bomb drops it will release bait making a trail.