Sea Wolf (Ocean Cleanup): the microbe game, step by step

Updated 28 September 2026

Sea Wolf, which some candidates call Ocean Cleanup, has you pick microbes to clean three polluted ocean sites in 30 minutes. The rules take a minute to learn; the traps are pacing and choices you cannot undo.

How a site works

Each site lists the conditions a good treatment needs: ranges for some measurable characteristics, and traits that are wanted or harmful. Candidate and prep-provider descriptions agree on this flow:

1. Choose what to measure. You pick two characteristics. Only those are visible for the microbes you then see, so choose the ones that rule out the most bad candidates.
2. Sort the microbes. One by one, you send each microbe to this site, keep it for the next site, or reject it.
3. Build a pool. You start with a few microbes already in the pool and add more over several rounds, each time picking one from a short list.
4. Choose the treatment. You pick three microbes whose combined characteristics fall in the site's ranges, with the wanted traits and none of the harmful ones.

At the second and third sites you first review the microbes you saved for them.

What candidates warn about

• Choices are final. "I put something in the wrong site and couldn't go back" is a common post. Read the numbers before you click.
• Running out on site 3. With three sites in 30 minutes, aim to leave the first site with about 20 minutes left and the second with about 10.
• Overthinking the final three. The treatment step is fairly mechanical once the pool is good. The judgement is in what you measure and what you keep.

How it is likely scored

The product score is the quality of each site's treatment: averages inside the ranges, wanted traits present, harmful ones absent. The process score is thought to reflect how sensibly you sorted and selected along the way. Neither weight is published.

CasesTrain is an independent practice tool. It is not affiliated with, endorsed by or connected to McKinsey & Company. McKinsey, Solve and the game names are used only to describe the test; they belong to their owners. What is written here comes from candidates' own public reports and McKinsey's public FAQ, and may change.