Keanu is the person closest to sea level, with an elevation of -2 meters. Others have elevations that are either significantly above or in one case, just slightly above sea level.
Step-by-step explanation:
The friend who is closest to sea level is the one with an elevation closest to 0 m. Let's compare the elevations to determine this:
Leilani is hiking at 952 m in elevation - This is quite high above sea level.
Keanu is snorkeling at -2 m in elevation - This is below sea level but very close to it.
Kiah is scuba diving at 608 m in elevation - This seems incorrect for scuba diving, as it's usually done below sea level, but as stated, this would be above sea level and not the closest.
Kanoa is enjoying a picnic at 4 m in elevation - This is above sea level but very close to it.
Comparing these elevations, Keanu is clearly the closest to sea level at -2 m, just a little below it. Thus, the correct answer is Choice B) Keanu.