On mobile, if you are looking at the ground and are sitting in a boat with chest and open the inventory with another boat with chest in your hand, you will place the boat with chest that is in your hand. 

Steps to reproduce

1. Load up the mobile version of Minecraft

2. Place a boat/boat with chest

3. Sit in the boat/boat with chest with a boat/boat with chest in hand

4. Open the inventory and then close it. 

Observed behaviour

You will place another boat/boat with chest and go into the inventory

Expected behaviour

The inventory should open and nothing else should happen

link to video below

https://youtu.be/Ty1oBtv7Ors