Corporate Captain reported unstable approach resulted in premature descent below traffic pattern altitude.

Narrative

Flying into ZZZ; we had determined that the weather would allow us to cancel IFR and proceed into the pattern for a VFR approach. After cancelling IFR we proceeded directly to the airport from the north. At the time; one aircraft had just landed; and there were no other aircraft in the pattern. As we proceeded towards the airport; we noted that our GTN 750 was showing around 15 miles 'Distance to Destination.' As we proceeded closer to the airport; we realized that we were much closer to the airport than this indication was showing.At this point we were probably about 3 miles from the airport; and I immediately pulled the power to idle and began configuring with flaps and gear. As we got closer to the airport; on an extended left base; I realized that we were too fast to make a safe approach; so I initiated a right hand 360 turn to slow down. As I started this turn I was at about 600' AGL. I noticed that I was over a marina area; and having previously read that this airport is noise sensitive; I began a slow climb up to around 900' AGL while in the right-hand turn. The turn ended up being mostly over water and after completing the turn; I configured with landing flaps and completed a normal; uneventful landing at ZZZ.Lessons learned:The weather was rapidly improving as we approached ZZZ; and at first; we thought we might have to fly an instrument approach; so we loaded the RNAV Rwy XX into our Garmin navigator. Even though we loaded the approach; we were navigating to the airport itself. The GTN 750 shows 'Distance to Destination' to include the instrument approach that is loaded into the box. As we approached the airport; we were busy visually identifying the airport and determining if we could cancel and fly a VFR pattern. In this high workload environment; we momentarily mistook 'Distance to Destination' for our direct distance to the airport (which; by the way; is shown up at the top of the GTN display). This caused us to delay slowing down and configuring the aircraft for landing. Once we determined that we had to do a 360 to slow down and configure; we were already quite low; 600' AGL. I should have climbed up to a normal 1500' pattern altitude during this maneuver; both for safety and to be more noise sensitive to the surrounding area.