Q.What effect does too much watering have on a tomato plant?
What effect does too much watering have on a tomato plant?

Certified GKH Gardening Expert
There will normally be some yellowing or browning, wilting or drooping and overall plant will look sickly. There may even be some rotting of vine growth. This article will also have general signs to look for in overwatered plants: https://www.gardeningknowhow.com/plant-problems/environmental/signs-of-plants-affected-by-too-much-water.htm

Overwatering also causes the tomatoes to split