Just to let you know in advance I am currently a Meteorology student and storm chaser at Oklahoma University.
Lightning is very dangerous, and even moreso on a lake as you are obviously the tallest structure around and water tends to conduct electricity very very well. It is very important to look up the expected weather for the day you are going fishing on that day, as it will give you an indication of whether or not storms may be present (it will also help you figure out patterns to fish behavior in different weather conditions). But as you said, you are on the bank.
If you notice the skies getting dark and something beginning to roll in, get away from the water IMMEDIATELY, not a lot of people realize lightning can hit in advance of a storm, some people say up to around 3 miles ahead in fact. Thunder is a pretty good indication of lightning, so keep an ear out.
The goal in a lightning storm is to NEVER be the tallest object in the area, as lightning looks for the fastest way into the ground, the tallest object is it. You need to find cover in a low lying area or safe house (vehicles work as you would not get zapped by the lightning inside of it), or ANYTHING as soon as possible.
One last thing of note, people that have been hit by lightning say your body can 'feel' the charges in the area before they build enough to strike... People note having their hair stand on end (body and otherwise), and a 'tingly' sensation. If you feel that it is already too late, drop to the ground asap and stick your rear in the air (no lie).
Be safe.
