That's a moray

The biggest species of moray eel that we encounter on Bonaire's reefs is the green moray. Although they get up to 8 feet, the ones that we have seen aren't quite that long.  Generally, they hide in reef recesses during the day, with only their heads visible.  Then at night, they forage in the open.

However, this green moray (over 5 feet long) was out swimming.  In fact, it swam quite near me, so I just kept taking photos of it.  This occurred at a depth of about 45 feet.