For create your own board game, these should be the steps:

1. Choose the kind of game (strategy, ability, luck, …or a mixture of all)
2. Choose a theme and write your idea. (Water is our theme but you can focus on a particular aspect)
3. Decide which are the tools for playing (cards, dice, turns,…)
4. Decide the age of the players
5. Decide the numbers of players
6. Draw the table
7. Draw the pieces
8. Draw the box

 For further ideas, read this link:

Make-Your-Own-Board-Game