You can click on this link and find over 70 cucumber salads and determine what fits your criteria for healthy: http://food52.com/recipes/tags/cucumber%20salad?page=1

And that's just the salads on the site! By typing just "cucumber" on the search you will find many more.

A sunomono salad. Slice seeded cucumbers thin, add some re-hydrated Wakame seaweed.
Dress with a good helping of rice vinegar, icewater (or dashi stock), a touch of sugar and a dash of soy sauce.
Some boiled shrimp or crab (or the fake crab) can be an addition.
It's better if soaks overnight and lasts few days in the 'fridge.

Can you be more specific as to what you mean by "healthy"? People have very different views on this! ;o)