I had spotted a family of Grebes with new-born chicks on the river near where I live but couldn't figure out how I could get close to them and at the desired low angle. The banks are high and steep and the Grebes stayed well in the middle of the river.
Then I realized we have a small rubber boat with an elektro motor so I persuaded my husband to drive the boat and me to the river.
Once afloat I took my time with the grebes, everytime overtaking them with a very wide turn, tying the boat to some reed stems and let the family swim past me on their own accord. I repeated that a couple of times and after a while they accepted that weird floating thing with the big 'pipe' sticking out as something harmless.