The evidence that spinosaurids were semi-aquatic now seems pretty
compelling, especially in light of isotopic data. While on the topic
of semi-aquatic theropods, there is also Andrea Cau's hypothesis that
the Madagascan abelisaurid _Majungasaurus_ was also semi-aquatic. The
topic was thrashed out in Darren Naish's blog a few years ago.
http://scienceblogs.com/tetrapodzoology/2009/06/aquatic_majungasaurus_or_not.php
Note in particular Andrea's comments in support (e.g., #17) and
Darren's comment #29, in which he concedes that relatively minor
osteological changes in certain non-avian theropod taxa might indicate
semi-aquatic habits.