I have seen similar effects on a visit to Shark Bay in Australia. The effects can be very impressive. They are indeed mirages, though some of the effects suggest more complicated mirages than most.

The main effects of mirages are the result of a low-lying layer of hot air. Any light entering such layers from the side tend to get bent upwards because the hot air and in particular any water vapour it contains, are less dense than the surrounding air and layers of air above it.

When a ray of light travels through any transparent material where the density differs in neighbouring layers, it bends towards the layers of higher density. If you want some diagrams showing the paths taken by light in a mirage, try doing an Internet search on the word "mirage", but you may be able to clarify the effect in your own mind by drawing a picture of a tower at one end of horizontal layers, and the paths of rays of light passing through those layers and bending upwards as they go.

If you draw it correctly you will see that the effect is rather like standing at one end of a horizontal mirror, or possibly a lakeside, and seeing objects on the other side both directly and inverted.

The picture is somewhat complicated by the fact that the layer of warm air is not a sharply defined surface like a mirror, but is fuzzy, which is why objects and their reflections are separated by a comparatively thick layer of distortion.

Under more complicated circumstances there might be multiple layers of air with warm air between layers of cooler air. That obviously complicates matters, with the light being bent in both directions and avoiding the warm air layer.

I do not think that this is a mirrage. To explain would be easy with a white board and a couple of markers but a little bit more difficult in words.

The refractive index of the atmosphere is determined mainly by the water vapour content. In a normal atmosphere the water vapour content falls as altitude increases. As the water vapour content falls, the refractive index falls. If a light wave is launched from an object parallel to a tangent to the earth's surface it will travel in a straight line and the earth's surface will fall away below it. In effect the light wave is climbing in altitude and hence climbing into an area of the atmosphere with a reduced refractive index. This causes the light wave to be refracted back towards the surface. This allows us to see a small way around the curvature of the earth.

It is good that you included the map showing surface atmospheric pressure. The high pressure over the area and the resulting low wind speeds allow water vapour evaporated from the sea to form a very humid layer near the surface. This means that the rate of change of refractive index with altitude increases. This in turn causes the angle of refraction to change and the light wave is bent back closer to the surface. In this case the refraction is such that you were able to see further around the curvature of the earth and well beyond the usual horizon.

The rather unstable image is caused by bubbles of air formed by heating at the surface rising through the atmosphere. The bubles of air have a different refractive index to the surrounding air which causes the instability.

The mirror images of the boats are just that, a reflection off a very flat calm area of sea.

In the tropics I have seen an Island about 100 miles away "pop up" over the horizon on very calm days.