Staying on yacht is certainly an unique experience for a stay in Lisbon taking into account sailing history! For those who would like to try something a little different it is certainly worth it from my personal opinion and I'm pleased with my stay.
Padrão dos Descobrimentos is directly by the entrance and a few hundred metres further along is Belém Tower. These two sites areon the top 10 must visit locations in Lisbon and are situated literally on the door step. You are also able to book sunset and other cruises by the entrance as well.
All in all if you're looking for a different experience and are used to the outdoor lifestyle or life on the water this would be an interesting option to go for.