Mentioned in the DWP intergrated investment program section 6.22 in passing is Special forces having a specialist watercraft
and more direct in 6.48 that a rivirine patrol craft would be acquired from around 2022 to increase tactical mobility in the littoral zone.
they already have specialist watercraft for the green/brown/grey
I suspect that the reference is about replacement of existing vessels
sometimes the DWP is more of a headache than a benefit as it doesn't provide references to impact against extant capabilties - which didn't appear in earlier iterations of the WP