If I set up a Guatemalan corporation, can I buy beachfront, lakefront or border-strip land through it?

No. A commercial guide suggests incorporating a company under Guatemalan law and buying through it as “the most common approach” for lakefront and beachfront property, only an OCRET lease,… and within the Art. 123 border strip the company must have shareholders who are Guatemalan by birth,… so a local corporation with foreign shareholders does not enable the purchase. The US State Department sums it up in its 2024 Investment Climate Statement: the law gives foreigners the same property rights as citizens, but bars owning land immediately adjacent to rivers, oceans and international borders.