Sea Wolf Microbe Math: How Does the Averaging Rule Work?

Part ofWhat Is McKinsey Solve? A Guide to Redrock, Sea Wolf and SFL

Sea Wolf scores the average of your three microbes on each attribute, so a single microbe can sit outside the site's range and still belong in the right trio. The fastest way to check is to multiply the range by three and add whole numbers: an average of 4 to 6 means a sum of 12 to 18. The easy ways to lose points are an arithmetic slip under the clock and a strong trio that quietly includes the forbidden trait. Below: the rule as plain math, a fixed checking order, a time plan, and three practice scenarios with every sum written out.

What is Sea Wolf?

Sea Wolf (also called Ocean Cleanup) is one of the games in McKinsey Solve, McKinsey's online screening assessment. Prep guides and candidate reports say a 65-minute invitation usually means Redrock and Sea Wolf, and an 85-minute invitation adds Sustainable Futures Lab. The McKinsey Solve guide covers the full format.

As reconstructed by prep guides, each Sea Wolf site follows the same flow:

ocean sites per game (reported)

3

Source: mconsultingprep.com

microbes in each final treatment

3

Source: myconsultingcoach.com

scale for each microbe attribute

1-10

Source: solvegamesguide.com

reported timer for all three sites

30 min

Source: psg-cracked.com

McKinsey says no preparation is needed for Solve, and the in-game tutorial does teach the rules. What practice changes is speed on the mechanical parts, and the averaging math is the most mechanical part of Sea Wolf.

How does the averaging rule work?

Each site lists a target range for three attributes. Attribute names vary between versions: guides report Density, Energy and Size, and this article uses Energy, Mobility and Density. The rule, as every guide we checked describes it: the average of each attribute across your three microbes must fall inside the site's range. No single microbe has to be in range.

Ranges: think in sums, not averages

Dividing by three under time pressure is where errors creep in. Multiply both ends of the range by three once, and you only ever need to add three whole numbers:

Two details make the sum test exact rather than approximate:

• Bounds are inclusive. Road to Offer and Case Prep both state that an average exactly on the minimum or maximum passes. A sum of exactly 18 passes a 4 to 6 range.
• Values are whole numbers. Reconstructions show each attribute as an integer from 1 to 10, so the sum is an integer too. A sum of 19 against a 12 to 18 window is an average of 6.33: out. You never need the decimal.

The consequence that trips people up: a microbe outside the range can be the right pick. An Energy of 10 is useless alone against a 7 to 8 range, but paired with a 6 and a 7 it gives a sum of 23, inside 21 to 24.

Desired and undesired traits

Each microbe carries one trait. StrategyCase lists four: Aerobic, Heat resistant, Hydrophilic and Light sensitive. Each site names one desired and one undesired trait:

Guides agree each site starts at 100% effectiveness and loses 20% per missed check. They disagree on whether two undesired-trait microbes cost 20% or 40% (MConsultingPrep says per microbe; PSG Cracked says once). Either way the target is zero, so the disagreement changes nothing in practice.

Elimination order: which constraint should you check first?

Check the cheapest, most decisive constraint first. Trait checks need no arithmetic and remove microbes outright, so they come before any sums.

1. Strike every undesired-trait microbe. One look at the trait label, no math.
2. Short-list desired-trait microbes. Your trio needs at least one, so start from these as anchors.
3. Write the three sum windows. Once per site.
4. Fill the tightest window first. A range one point wide (such as 6 to 7) allows only 4 passing sums; a range two points wide allows 7. Also treat a range as tight when it sits far from most of your pool, for example a Mobility range of 8 to 9 when most of your microbes are around 5.
5. Check the other two sums. When you swap one microbe, adjust each running total by the difference instead of adding all three values again.
6. Stop at 100%. As reported, each check is pass or fail, so a trio in the middle of every range scores the same as one on the edge.

The same logic applies earlier in the site. When you sort microbes and pick prospects, you are choosing future trio partners, so keep a spread of high and low values on the attribute with the tightest range instead of keeping only microbes that sit inside it.

How much time should you spend per site?

Candidates and prep guides report one timer of about 30 minutes for all three sites (Leland, via Harvard's career center, says 30 to 35). McKinsey does not publish a per-site split, so treat this as a practice plan:

Why protect site 3: StrategyCase reports that an unfinished site scores zero regardless of the earlier sites. An 80% trio at each of three sites beats a perfect site 1 and an empty site 3.

Can you solve these 3 Sea Wolf practice scenarios?

These are original scenarios written for this article, not items from the real test. Try each before reading the solution.

Scenario 1: find the valid trio

Site ranges: Energy 4 to 5 (sum 12 to 15), Mobility 6 to 7 (sum 18 to 21), Density 2 to 3 (sum 6 to 9). Desired: Aerobic. Undesired: Light sensitive.

Solution. Strike M3 first. Its numbers are perfect, which is why it is a trap. Anchors: M1, M5, M8. The tightest window is Mobility (one point wide, sums 18 to 21). Start with M1 (Mobility 7) and look for two partners whose Mobility adds to 11 to 14: M2 + M4 gives 13.

• Energy: 5 + 7 + 3 = 15, inside 12 to 15 (exactly on the inclusive maximum)
• Mobility: 7 + 8 + 5 = 20, inside 18 to 21
• Density: 3 + 2 + 4 = 9, inside 6 to 9 (again on the maximum)
• Aerobic present, no Light sensitive: 100%

A brute-force check of all 56 possible trios finds six that score 100%. You need one, so stop at the first. Now look at M5: it is an Aerobic anchor, but its Energy of 8 and Density of 6 push two sums over at once. M1 + M4 + M5 sums to 16 on Energy and 13 on Density, for 60%. No 100% trio contains M5.

Scenario 2: the out-of-range microbe you need

Site ranges: Energy 7 to 8 (sum 21 to 24), Mobility 3 to 5 (sum 9 to 15), Density 5 to 6 (sum 15 to 18). Desired: Heat resistant. Undesired: Hydrophilic.

Solution. Strike C. Anchors: A and E. Two windows are one point wide (Energy and Density). E looks strongest because its Energy is already in range, but its Density of 10 leaves the other two microbes only 5 to 8 of Density between them. The two lowest remaining Density values are D (4) and A (5), which sum to 9, so no trio with E can pass Density. Take A instead. Checking A's partners on the Energy window (15 to 18 still needed) points to B + F:

• Energy: 6 + 10 + 7 = 23, inside 21 to 24 (A is below the range and B is above it, but together they pass)
• Mobility: 4 + 2 + 5 = 11, inside 9 to 15
• Density: 5 + 6 + 5 = 16, inside 15 to 18
• Heat resistant present, no Hydrophilic: 100%

Scenario 3: when 100% is not available

Site ranges: Energy 2 to 3 (sum 6 to 9), Mobility 8 to 9 (sum 24 to 27), Density 3 to 5 (sum 9 to 15). Desired: Light sensitive. Undesired: Aerobic.

Solution. Strike R, even though it would help both tight sums. P is the only desired-trait microbe, so it belongs in the trio. The trios with P and without R:

No trio reaches 100%. Dropping P (for example Q + T + U) or keeping R (P + Q + R) also caps out at 80%, because each gives up a trait check instead of a range. Submit an 80% trio and move on. The real lesson sits earlier in the site: one more non-Aerobic microbe with Energy 3 or less, Mobility 7 or more and Density between 2 and 8, kept during sorting, would have completed P + Q for 100%. That is why sorting and prospecting should keep extremes on your tightest attribute.

Where can you practice the averaging rule?

DrillCase's McKinsey Solve practice includes a Sea Wolf task built for familiarization. Each run draws new sites and microbes, and after you submit, the results table shows the best trio available in your pool next to the one you chose, with the average for every check. Use it to rehearse the elimination order and the time checkpoints until they are automatic.

Practice tools are for the weeks before the test. McKinsey expects candidates to take Solve "alone, without assistance from others" and bans apps, websites and AI tools, so nothing here is meant for use during a live assessment. For what the scores mean afterward, read how McKinsey Solve is scored. You can also browse all McKinsey practice scenarios or the Solve overview.

What should you check at each Sea Wolf stage?