To determine the correct statements regarding ocean temperature, let's analyze each statement provided:

1. Statement A: "The maximum and minimum annual temperatures of ocean water are recorded in August and February respectively in the northern hemisphere."
   This statement is accurate. In the northern hemisphere, ocean temperatures are usually highest in August after the summer months and lowest in February following winter.
2. Statement B: "The Atlantic ocean records lower annual range of temperature than the Pacific ocean."
   This statement is incorrect. Generally, the annual range of temperature is influenced by factors such as ocean currents, latitude, and surrounding landmasses. The Pacific Ocean, due to its vastness and exposure to both polar and tropical influences, tends to have a varied range of temperatures over the year compared to the Atlantic.
3. Statement C: "Annual range of temperature is higher in the enclosed sea than in the open sea."
   This statement is true. Enclosed seas, such as the Mediterranean, often have larger temperature ranges due to lesser mixing with open ocean waters and more significant influence of surrounding land temperatures.
4. Statement D: "The isotherms are not regular and do not follow latitudes in the northern hemisphere."
   This is also correct. Isotherms, which are lines of equal temperature, do not strictly follow latitudinal lines, especially in the northern hemisphere, due to factors such as land-sea distribution, ocean currents, and wind patterns.

Based on the analysis above, the correct statements are A, C, and D. Thus, the correct answer is: