gatt wrote:
Isn't taking scuba divers flying sort of dangerous?

It can be, depending on how much diving they did, what the depth
profiles were, what air tank mixes they used (if different from normal),
and how long they waited before climbing in to the airplane. It also
depends on how high you fly.

The general FAA suggestion from the AIM in 8-1-2 Section d item 2 is

"2. The recommended waiting time before going to flight altitudes of up
to 8,000 feet is at least 12 hours after diving which has not required
controlled ascent (nondecompression stop diving), and at least 24 hours
after diving which has required controlled ascent (decompression stop
diving). The waiting time before going to flight altitudes above 8,000
feet should be at least 24 hours after any SCUBA dive. These recommended
altitudes are actual flight altitudes above mean sea level (AMSL) and
not pressurized cabin altitudes. This takes into consideration the risk
of decompression of the aircraft during flight. "

These are very general recommendations. A SCUBA diver proficient in
high altitude lake diving may have better knowledge about the risks they
are taking.