How they can be harassed by humans while in a resting phase, aggressive swimmers who pursue the dolphins as they slowly rise to the surface to breathe cause the dolphins to have to move their tail flukes more energetically than they ordinarily would--i.e., the swimmers cause the dolphins to waste energy at a time when they are resting and trying to recoup energy for the next night's feeding journey. They are not interested in interaction during rest periods and will actively avoid swimmers during such times--you are right, they can easily avoid us, but they have to spend energy in order to do it at a time when they are trying to recoup energy, and that, to me, constitutes harassment.
Also, swimming directly and aggressively at dolphins when they are moving slowly can cause them to startle or shake, then quickly leave, and that, to me, constitutes harassment.
Approaches to dolphins should be respectful, gentle, indirect, hands and arms at your sides, etc., and they may reward you with a remarkable encounter. Otherwise, your approach to them may well constitute harassment.
Even if you never get near them, if your approach causes them to leave the area where they had chosen to be, or otherwise interferes with their patterns, then, from my point of view, you are harassing them.
If you are lucky enough to see dolphins in the wild please remember these simple rules:
* Do not harass the dolphins-give them space.
They are very powerful animals and are not there for your amusement.
* Never attempt to feed a wild dolphin.
It is illegal and could easily result in the dolphins death through incorrect food or bacteria in the fish.
* Do not throw rubbish in the ocean or on the beach, and please clean up any that you see.
Many dolphins die from swallowing foreign objects.
* Many dolphins are injured by boat motors.
Make sure the boat you are in drives carefully near dolphins