Based on the picture and the location you give, it could be Ceiba pentandra. There are quite a few species with similar buttress root systems (examples are Ficus macrophylla, Heritiera littoralis, and various Terminalia species).

BTW, where exactly in Costa Rica is this tree located?

You must travel a lot, because I know I've seen you post stuff from a lot of different places lately.

Thanks, I think it probably is a Kapok Tree.

And, I do travel a bit...although this pic was not taken by me, so don't know where in Costa Rica it's from.

Here is a link that might be useful: Kapok Tree (Ceiba pentandra)