Final answer:
In an estuary where tidal currents are strong and river flow is low, a saltwater estuary is most likely to occur due to the dominance of salty sea water from the tides.
Step-by-step explanation:
If tidal currents are strong in an estuary while river flow is very low, the type of estuary that is most likely to occur is a saltwater estuary. Tidal currents introduce a large amount of salt water into the estuary, which, due to the low river flow, would not be sufficiently diluted by fresh water.
As a result, the estuary would have a higher salinity resembling that of the incoming tidal waters rather than a brackish mix of salt and fresh water. This scenario does not support the formation of a freshwater estuary due to the dominance of salty sea water during strong tides.
A mixed estuary, which involves a more even blend of salt and fresh water, is also less likely to occur in such conditions. While 'tidal estuary' describes the influence of tides, it does not exclusively characterize the type of water present, making 'saltwater estuary' the most apt description.