These are my favorite style of Pelican shots. This is all about location. A low boat is a requirement. In flight photos like this mean you need to be at the same level as the big bird flying by (or around you).
Once or twice a year we will go out to the small islands / keys, at high tide, and float just off shore. The birds don’t pay any attention since you are floating around with them and not anywhere close to nests.
Now, the boat is bouncing and the birds flying, so the rule is bring plenty of batteries and memory cards. There will be many more misses than usual. Ultimately though you will have plenty of amazing photographs not to mention a great adventure.
Coastal South Carolina.