i’m going on a blue shark day trip snorkelling only with blue sharks in july

curious what you all advise about using strobes. it would be much simpler using natural light but would some fill in make the pictures much better?

the attached images from the tour company website

my thoughts are:

if no strobes i can use program or similar to get fast shutter speed with available light- also much easier bobbing about near the surface without a big rig

downside is that it might be a dark day - slower shutter speeds - and underneath of sharks could be very dark

i can’t work out from the images if flash has. been used