Thank you for your replies, LittleStain and zenox98. The examples are great, but I'm new to Construct 2 and I'm not really sure how to modify the examples zenox98 was nice enough to link to.
My game is a grid based puzzle game and the water trail needs to be present at all times under the player, and be transparent enough to see and interact with other sprites the player walks over or next to, so overlapping sprites used for the trail in the examples won't work, because of the transparency. I don't think a particle trail would work either, because I think the objects used overlap too? Not sure about that.
What I'm asking for really is ideas or theory about how it can be done. I'm thinking the player comes in contact with a new floor sprite on a grid, it creates a new water sprite on it. As the player moves along, the created water sprite starts a timer for 5 seconds, then changes to a sprite with an evaporation animation, then deletes itself once the animation ends. The water sprite also detects if it's next to another created water sprite and switches to a version of the sprite that makes the water trail look like it seamlessly flows together.
Sorry if my explanation is hard to understand. I can see it clearly in my mind, but it's hard to put into words, and even harder for me to implement. I would be very grateful if I could receive some additional help with this matter.
I'll experiment more with this on my own, but I feel like I hit a wall.
Edit: Is there a decent image file hosting site I can use to post images on this forum? Maybe some sketches would help?