To cut it into small chunks:

1. Rinse the watermelon really well under cold running water and then pat it dry with a paper towel.
2. Cut it in half with a sharp knife and place the flat side on the counter. Starting from the top, take off the rind with the knife guiding yourself with the white part of the rind. Finally, cut off the top part and remove any white areas you may have missed.
3. Cut both halves in half to end up with a total of 4 pieces. Then, cut each piece into slices as thick as you want and make vertical and horizontal cuts to each slice to end up with small chunks.

To cut it into triangles:

1. Rinse the watermelon really well under cold running water and then pat it dry with a paper towel.
2. Cut it in half with a sharp knife and then cut both halves two more times to end up with a total of 8 pieces. Now you can cut each piece into slices as thick as you want to end up with small triangles.